Based, as usual, on a false premise.
Namely, that the Bible is a comprehensive compendium of everything related to the moral, theological and juridical nature of the Christian life. It isn't.
The phrase ...."where does it say that in the Bible?".....is so trite and vacuous.
As the Evangelist tells us.."But there are also many other things which Jesus did; which, if they were written every one.....
The Bible says nothing about abortion, artificial contraception, masturbation, in vitro fertilization and numerous other things.
As a previous poster pointed out, annulment is a judgement that a valid marriage never occurred. That is all. It's not a "Catholic divorce".
It's unclear to me why anyone would even expect that to be mentioned in the Bible.