Genesis 3:19

Gesenius thinks that this is a rare use of the conjunction כִּי for (#3588) as a relative pronoun, i.e. “the Ground which from her you have been taken which a dust is yourself.” Also Gen. 4:25 as the KJV renders it, “For God, said she, hath appointed me another seed instead of Abel, whom Cain slew.” Take note of this every time you see the word “for” as it might lend a hint to something. Many describe the word as having a wide variety of applications—because, that, if, etc. Much of the time it is guesswork, “Note. — כִּי is sometimes of difficult and uncertain interpretation, and in some of the passages quoted a different explanation is tenable. Authorities especially read the Hebrew differently, when the choice is between for and yea.” -BDB