en_tn/gen/17/20.md

As for Ishmael

The words "As for" show that God is switching from talking about the baby that would be born to talking about Ishmael.

Behold

"Look" or "Listen" or "Pay attention to what I am about to tell you"

will make him fruitful

This is an idiom that means "will cause him to have many children." (See: rc://en/ta/man/translate/figs-idiom)

will multiply him abundantly

"I will cause him to have many descendants"

leaders of tribes

"chiefs" or "rulers." These leaders are not the twelve sons and grandsons of Jacob that will lead the twelve tribes of Israel.