Genesis 4:25

And Adam knew his wife again
The Targum of Jonathan adds, at the end of a hundred and thirty years after Abel was killed, see ( Genesis 5:3 ) but, according to Bishop Usher, Seth was born the same year, which is most probable.

And she bare a son, and called his name Seth,
that is, "put, placed, set"; not with any respect to Cain, who had no settled fixed abode, but wandered about; or to Seth as a foundation of the church and true religion, being a type of Christ the only foundation, though he may be considered in such a light; but the reason of his name follows:

for God, [said she], hath appointed me another seed instead of
Abel, whom Cain slew;
that is, another son in his room; and by calling him a "seed", she may have respect unto the promised seed, whom she once thought Cain was, or however expected him in his line, as being the firstborn; but he proving a wicked man, and having slain his brother Abel, on whom her future hope was placed, has another son given her, and substituted in his room, in whom, and in whose family, the true religion would be preserved, and from whom the Messiah, the promised seed, would spring see ( Galatians 3:16 ) .