en_tn/gen/21/30.md

you will receive

"you will take"

from my hand

Here "hand" stands for Abraham. AT: "from me" (See: rc://en/ta/man/translate/figs-synecdoche)

it may be a witness

The word "it" refers to the gift of seven lambs.

so that it may be a witness for me

The abstract noun "witness" can be stated as "to prove." AT: "to prove to everyone" (See: rc://en/ta/man/translate/figs-abstractnouns)