In Revelation 14, Jesus and 144,000 Christians are found standing in God’s presence on Mount Zion. They join God and the other spiritual beings of God’s Heavenly courtroom in singing a beautiful song. It’s there that an interesting note is made about the 144,000: “It is these who have not defiled themselves with women, for they are virgins.”
Many liken this comment to a purity ritual related to Old Testament laws for war. This is an appropriate possibility, but there’s another interpretation that also fits the bill quite well, especially since this purity ritual would really be a reference to temporary abstinence from sex, not virginity.
Popular Jewish apocalyptic literature like 1 Enoch had a big focus on the story of the spiritual beings of Genesis 6—that is, the “sons of God” who left Heaven to procreate with human women, which gave rise to creating the Nephilim (the giant race of the Old Testament from which Goliath descended from).
That being said, John’s point in Revelation 4 may very well be that these new spiritual beings in God’s presence—these new resurrected human “sons of God”—don’t overstep their boundaries and sin against God like the old “sons of God” did. Resurrected Christians are faithful to God and are the replacement plan of God’s old fallen family.