Hello Nathan, I believe the Scriptures you are looking for are/is Genesis 6:1-4
1) And it came to pass, when men began to multiply on the face of the earth, and daughters of men were born unto them.
2) That the sons of God saw the daughters of men that ther were fair; and they took them wives of all which they chose.
3) And 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.
4) There were giants (Nephilim) 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.
There are two schools of thought on this:
1) The sons of God were Seth's descendant who married the daughters of men who were Cains descendant. Most believers follow this view today.
2) The sons of God were angels who married the daughters of men. Most in the early church believe this view.
Those in the second school of thought on this issue use I Corinthians 11:10, "For this cause ought the woman to have power on her head because of the angels." Saying Paul the Apostle warn of this event repeating itself.
But please let me caution you I believe as you do in the second school of thought but it really is of no importance (and hard to prove) when compare to what Paul said he delivered first of all.I Corinthians 15:3-4
3) For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures.
4) And that He was buried, and that He rose again the third day according to the scriptures:"
This is why Jesus told the Pharisees and other Jews, "Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of Me." (John 5:39) I'm sure you know this but what does Christ do for us I Peter 3:18, " For Christ also hath once suffered for sins, the just for the unjust, that He might bring us to God, being put to death in the flesh, but quickened by the Spirit." quickened means to be made alive. This is the most important message we can preach!