There were quite a number of factors that had led up to the great flood. First one must recognize some of the participants that contributed to this. These factors led YHWH to grieve and feel pain in his heart that he had ever made mankind!
2) The Nephilim - ( Giants )
3) The Mighty Men of Renown
4) The Sons of God
5 The Lord saw how great man's wickedness on the earth had become, and that every inclination of the thoughts of his heart was only evil all the time. 6 The Lord was grieved that he had made man on the earth, and his heart was filled with pain. 7 So the Lord said, "I will wipe mankind, whom I have created, from the face of the earth - men and animals, and creatures that move along the ground, and birds of the air - for I am grieved that I have made them." Gen 6:5-7 ( NIV )
NEPHILIM - GIANTS & THE MEN OF RENOWN.
When men began to increase in number on the earth and daughters were born to them, 2 the sons of God saw that the daughters of men were beautiful, and they married any of them they chose. 3 Then the Lord said, "My Spirit will not contend with man forever, for he is mortal; his days will be a hundred and twenty years."
4 The Nephilim were on the earth in those days and also afterward when the sons of God went to the daughters of men and had children by them. They were the heroes of old, men of renown. Gen 6:1-4 NIV
In the first two cases the Revised Version (British and American) changes "giants" into the Hebrew words "Nephilim ," Nephilim , and "Rephaim," repha'im, respectively. The "Nephilim of Gen 6:4 are not to be confounded with the "mighty men" subsequently described as the offspring of the unlawful marriages, of "the sons of God" and "the daughters of men." It is told that they overspread the earth prior to these unhallowed unions. That the word, whatever its etymology, bears the sense of men of immense stature is evident from the later passages; Num 13:33. The same is true of the "Rephaim," as shown by the instance of Og (Deut 3:11; Josh 12:4). There is no doubt about the meaning of the word in the case of the giants mentioned in 2 Sam 21 and 1 Chron 20.
This word, translated "giants" in the King James Version, but retained in the Revised Version (British and American), is found in two passages of the Old Testament-one in Gen 6:4, relating to the antediluvians; the other in Num 13:33, relating to the sons of Anak in Canaan. In the former place the Nephilim are not necessarily to be identified with the children said to be borne "the daughters of men" to "the sons of God" (verses 2,4); indeed, they seem to be distinguished from the latter as upon the earth before this unholy commingling took place. But it is not easy to be certain as to the interpretation of this strange passage. In the second case they clearly represent men of gigantic stature, in comparison with whom the Israelites felt as if they were "grasshoppers." This agrees with Gen 6:4, "the mighty men that were of old, the men of renow." Septuagint, therefore, was warranted in translating by gigantes.
SONS OF GOD
(Old Testament) (bene ha-'elohim, "sons of God" (Gen 6:2,4; Job 1:6; 2:1); bene 'elohim, "sons of God" (Job 38:7); bene 'elim, "ye mighty," the King James Version; "ye sons of the mighty," King James Version margin, the Revised Version (British and American); "sons of God" or "sons of the gods," the Revised Version margin (Ps 29:1); "sons of the mighty," the King James Version and the Revised Version (British and American); "sons of God" or "sons of the gods," the Revised Version margin (Ps 89:6 (7 in Heb)); Septuagint huioi tou theou, hoi aggeloi tou theou (Gen 6:2); huioi tou theou (Gen 6:4); hoi aggeloi tou theou (Job 1:6; 2:1); aggeloi mou (Job 38:7); huioi theou (Ps 29:1; 89:6; compare Dan 3:25)):
1. Job and Psalms: This article will deal with this phrase as it is used in the above passages. In the passages from Job and Psalms it is applied to supernatural beings or angels. In Job the "sons of God" are represented as appearing before the throne of Yahweh in heaven, ready to do Him service, and as shouting for joy at the creation of the earth, In the Psalms they are summoned to celebrate the glory of Yahweh, for there is none among them to be compared to Him. The phrase in these passages has no physical or moral reference. These heavenly beings are called "sons of God" or "sons of the 'elohim" simply as belonging to the same class or guild as the 'elohim, just as "sons of the prophets" denotes those who belong to the prophetic order.
2. Gen 6:2,4: Different views, however, are taken of the passage in Gen 6:2,4: "The sons of God saw the daughters of men that they were fair; and they took them wives of all that they chose ..... The Nephilim were in the earth in those days, and also after that, when the sons of God came in unto the daughters of men."
(1) "Sons of God" is interpreted as referring to men, (a) to sons of the nobles, who married daughters of the common people. This is the view of many Jewish authorities, who hold that it is justified by the use of 'elohim in the sense of "judges" (Ex 21:6; 22:8 f, etc.). But this cannot be the meaning of 'elohim here, for when 'adham, "men," is used to denote the lower classes, it is contrasted with 'ish, as in Ps 49:2 (3 in Heb), not with 'elohim. When contrasted with 'elohim it signifies the human race. (b) Some commentators hold that by "sons of God" is to be understood the pious race descended from Seth, and by "daughters of men" the daughters of worldly men. These commentators connect the passage with Gen 4:25 f, where the race of Seth is characterized as the worshippers of Yahweh and is designated as a whole, a seed (compare Deut 14:1; 32:5; Hos 1:10 (2:1 in Heb)). They consider the restricted meaning they put upon "men" as warranted by the contrast (compare Jer 32:20; Isa 43:4), and that as the term "daughters" expresses actual descent, it is natural to understand "sons" in a similar sense. The phrase "took wives," they contend also, supports the ethical view, being always used to signify real and lasting marriages, and cannot, therefore, be applied to the higher spirits in their unholy desire after flesh. On this view verses 1-4 are an introduction to the reason for the Flood, the great wickedness of man upon the earth (verse 5). It is held that nothing is said in verse 4 of a race of giants springing from the union of angels with human wives (see paragraph 2, below), and that the violence which is mentioned along with the corruption of the world (verse 11) refers to the sin of the giants.
(2) Most scholars now reject this view and interpret "sons of God" as referring to supernatural beings in accordance with the meaning of the expression in the other passages. They hold that Deut 14:1, etc., cannot be regarded as supporting the ethical interpretation of the phrase in a historical narrative. The reference to Jer 32:20, etc., too, is considered irrelevant, the contrast in these passages being between Israel and other nations, not, as here, between men and God. Nor can a narrower signification (daughters of worldly men) be attached to "men" in verse 2 than to "men" in verse 1, where the reference is to the human race in general. This passage (Gen 6:1-4), therefore, which is the only one of its kind, is considered to be out of its place and to have been inserted here by the compiler as an introduction to the story of the Flood (verses 5-8). The intention of the original writer, however, was to account for the rise of the giant race of antiquity by the union of demigods with human wives. This interpretation accords with Enoch chapters 6-7, etc., and with Jude 6 f, where the unnatural sin of the men of Sodom who went after "strange flesh" is compared with that of the angels (compare 2 Peter 2:4 ff). (See Havernick, Introduction to the Pentateuch; Hengstenberg on the Pentateuch, I, 325; Oehler, Old Testament Theology, I, 196 f; Schultz, Old Testament Theology, I, 114 ff; Commentary on Genesis by Delitzsch, Dillmann, and Driver.)
Sin and the Flood.
That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
The sons of God (bene 'Elohim)... daughters of men. Wickedness was increasing on every hand. Cain's descendants became exceedingly godless and pagan. A powerful race of giants, called "Nephilim ," came into prominence. The verb (napal), "to fall," has been considered the source of the noun, and so these gigantic creatures have been thought of as "fallen ones." The reference to the (bene 'Elohim) has occasioned marked differences of opinion among scholars. ('Elohim) is plural in form. It is usually translated "God." But it can be translated "gods," as, for instance, when it refers to the gods of the heathen neighbors of Israel. It can, also, denote the heavenly circle of beings in close fellowship with Jehovah, residents of heaven, assigned specific duties as God's assistants (see Job 1:6). In some cases in Scripture "sons of God" may be identified with "angels" or "messengers." Jesus is the Son of God in a unique sense. Believers are called "sons of God" because of their relationship to him. In the OT, however, "sons of God" are a special class of beings that make up the heavenly court.
The reference to the marriages of (bene 'Elohim) to the daughters of men has been dealt with in many ways. To translate it literally would make the passage say that members of the heavenly company selected choice women from the earth and set up marriage relationships with them, literally and actually. This can be the only interpretation of Jude 1:6. There, the (bene 'Elohim) were plainly the members of God's heavenly court. S. R. Driver maintains that this is the only legitimate and correct sense that can be accepted. Jesus' reply to the Sadducees, in Matt 22:30, seems to make this view untenable. He said that the angels "neither marry nor are given in marriage." The statement in Gen 6:2 makes it clear that permanent marriage is described. Women were chosen and forced to become parties to the unnatural relationship. Bible students who have rejected this solution have resorted to other explanations. Some have said that a union of Seth's godly line with Cain's godless descendants is described. Still others hold that these words refer to marriage between persons of the upper class of society and those of a lower or less worthy class.
In the light of the facts and the accurate rendering of the words of the text, we conclude that some of the heavenly group (angels or messengers) actually took wives of the earthly women. They used superior force to overpower them, to make the conquest complete. The "sons of God" were irresistible (cf. 2 Peter 2:4; Jude 6).
Hence, if these "sons of God " were merely men, the question arises, why were their offspring "men of renown" more than those of the wicked, or the of faithful Noah? Given many of the above facts and a deep look into the Hebrew and Greek writings... the "sons of God" mentioned at Genesis 6:2, must have been angels, spirt "sons of God." This expression is applied to angels at Job 1:6: 38:7.
This view is supported by Peter who speaks of "the spirts in prison, who had once been disobedient when the patience of God was waiting in Noah's days, while the ark was being constructed," ( 1 Pet. 3:19, 20 ) NWT
as another bible version puts it
" also he went and preached to the spirits in prison who disobeyed long ago when God waited patiently in the days of Noah while the ark was being built. In it only a few people, eight in all, were saved through water, NIV ( 1 Peter 3:19-20 )
Also Jude writes of " and the angels that did not keep their original position but forsook their own dwelling place he has reserved with eternal bonds under dense darkness for the judgment of the great day. " ( Jude 6 ) NWT
as another bible version puts it
" and angels who did not keep their own domain, but abandoned their proper abode, He has kept in eternal bonds under darkness for the judgment of the great day " ( Jude 6 ) NASB
Angels had the power to materialize in human form, and some angels did so to bring messages from God. (Gen. 18:1, 2, 8, 20-22: 19: 1-11; Josh, 5:13-15, and many other texts). But heaven is the proper abode of spirt persons, and the angels there have positions of service under YHWH. (Dan. 7: 9, 10) To leave this abode to dwell on earth and to forsake their assigned service to have fleshly relations would be rebellion against God's laws.