1 Enoch 6:2
1 And it came to pass when the children of men had multiplied that in those days were born unto them beautiful and comely daughters. 2 And the angels, the children of the heaven, saw and lusted after them, and said to one another: 'Come, let us choose us wives from among the children of men and beget us children.' 3 And Semjâzâ, who was their leader, said unto them: 'I fear ye will not indeed agree to do this deed, and I alone shall have to pay the penalty of a great sin.' 4 And they all answered him and said: 'Let us all swear an oath, and all bind ourselves by mutual imprecations not to abandon this plan but to do this thing.' 5 Then sware they all together and bound themselves by mutual imprecations upon it.
Tertullian Against Marcion 5.18
For He did not forbid (our first parents) a taste of the miserable tree, from any apprehension that they would become gods; His prohibition was meant to prevent their dying after the transgression. But the spiritual wickedness did not signify the Creator, because of the apostle's additional description, in heavenly places; for the apostle was quite aware that spiritual wickedness had been at work in heavenly places, when angels were entrapped into sin by the daughters of men. But how happened it that (the apostle) resorted to ambiguous descriptions, and I know not what obscure enigmas, for the purpose of disparaging the Creator, when he displayed to the Church such constancy and plainness of speech in making known the mystery of the gospel for which he was an ambassador in bonds, owing to his liberty in preaching — and actually requested (the Ephesians) to pray to God that this open-mouthed utterance might be continued to him?
Notes and References
"... The Latin church father Tertullian associates 1 Corinthians 11:10 with the tradition of the fall of the Watchers from Genesis 6. The veil was to designate them as married women and therefore unavailable, for the unveiled heads of virgins he considered particularly enticing to the angels. (There are similar references in Corona 14:2; Against Marcion 5.8.2; and On Prayer 22.5-6) ..."
Lewis, Scott M. "'Because of the Angels': Paul and the Enochic Traditions" in Harkins, Angela Kim, et al. (eds.) The Watchers in Jewish and Christian Traditions (pp. 81-90) Fortress Press, 2014