"explain according to the scripture Without any own explanation?"
I could just post the scripture below and leave it at that but apparently that has proven to be difficult for readers since they don't all agree which is why you started the thread.
1And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
2That the sons of God saw the daughters of men that they
were fair; and they took them wives of all which they chose.
3And the LORD said, My spirit shall not always strive with man, for that he also
is flesh: yet his days shall be an hundred and twenty years.
4There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare
children to them, the same
became mighty men which
were of old, men of renown.
So in an intellectually honest attempt to understand this passage of scripture it would be within the parameters of "explain according to the scripture" to consider everything that has been written in Genesis in previous chapters to shed light on this. Let us start there before we try to find meaning by looking in other books of the bible. The immediate context is always the first to be considered in proper hermeneutics (the philosophy and methodology of text interpretation, especially the interpretation of biblical texts, wisdom literature, and philosophical texts). When we encounter the phrase
sons of God here and naturally ask ourselves "what is this? Who are the sons of God? Did I miss something in a previous chapter up to this point?" So we turn back and sure enough we find Gen 4:26 And to Seth, to him also there was born a son; and he called his name Enos:
then began men to call upon the name of the LORD. If you have a KJV with marginal notes you will see it also say or "by the name of the Lord". So based on this context I would think that Gen 6 is not explaining who the Sons of God are because they have already been mentioned in Gen 4. In Gen 4 a list and description of Cains people and civilization he was building in the Land of Nod was given and then it talks about the lineage of Seth which is the civilization that Adam is building separate from Cains people. So you have 2 camps of people in the earth. The sons of men (Cain's people) and the sons of God (Adams people). Now when the sons of God saw the daughters of men (women who were in Cain's camp) that they were fair; and they took them wives of all which they choseThis suggest that the women made themselves look better than the women in the sons of god camp. Maybe by makeup and sensual dress. The "took them wives of all which they chose" suggest polygamy which had already begun according to Gen 4 and Lamech so again sticking with the context we are on safe ground with these conjectures. This marrying or mixing with the ungodly women of Cains camp causes a sinful corruption so that the sons of god become evil and eventually only Noah is left. Why did they start calling themselves by the name of the Lord (sons of God) in Gen 4:26 it was because Cains people were not godly and did not want God. We know that Enoch prophesied about the coming of the Lord and judgement against the ungodly from the book of Jude. Who was Enoch talking about when he said ungodly? Cains camp most likely. And they were probably persecuting Adams camp the sons of god (godly people who believed in a coming Lord.) As we continue to read we find that Enoch walked with God and was translated, and eventually only Noah is left. We can understand this based on the context of Gen 1-6 but we have to go beyond the context to squeeze in a fallen angel mating with men theory. The truth that God forbids the godly men to not mix with ungodly women or take foreign wives in the case of Israel, continues throughout the bible and even into the new testament with the command not to be unequally yoked, fellowship with darkness, etc. Also Jesus said that Angels do not marry or have sex. By making that statement it is clear that Jesus rejected this view that angels had sex with women in Gen 6. That statement from Jesus should put to rest the theory of angels having sex with women but for some reason people want this theory or myth to be true. There is no lesson to learn from the fallen angel story and nothing that we can apply to our lives. However the truth about the godly being corrupted by the ungodly is a truth stream that continues throughout the bible and we can learn much by examine this case of "the law of first reference" about this truth seen here in Gen 6. Now people will continue to hold to this view that angels mixed with men and created some kind of mutants and I am not sure why. People will even live with an ungodly girlfriend and not be convicted of it while speaking at length about the Angels and women making giant mutants and argue with you all day that they understand this correctly and that I am wrong. Yet they will not see that they are not a son of god and have been corrupted and are blind to their fornication living with their ungodly girlfriend. Because they can believe in the angel theory without it requiring any self examination or lesson in godly living. However if they accept the view that this story is about fornication with ungodly women that will require them to have to repent and turn from their sins.