John Gill Commentary 1 Samuel 18:26

"And when his servants told David these words, it pleased David well to be the king`s son-in-law. And the days were not expired;" — 1 Samuel 18:26 (ASV)

And when his servants told David these words
That the king desired no other dowry than an hundred foreskins of the Philistines:

it pleased David well to be the king's son in law ;
on such conditions; partly because of the honour of it, and partly because of his love to Michal; and chiefly because it would give him an opportunity of destroying the enemies of God, and of his people, as well as such a match would lead the way, and be a step in Providence to ascend the throne designed for him in due time:

and the days were not expired ;
neither for the bringing in of the foreskins, nor for the consummation of the marriage.