en_tn/gen/26/23.md

multiply your descendants

“will cause your descendants to increase greatly” or “will cause your descendants to be very many”

for my servant Abraham's sake

"for my servant Abraham" or "because I promised my servant Abraham that I would do this." (See: rc://en/ta/man/translate/figs-explicit)

Isaac built an altar there

Why Isaac built an altar can be made explicit: "Isaac built an altar there to sacrifice to Yahweh."

called on the name of Yahweh

"prayed in the name of Yahweh" or "worshiped Yahweh." See how you translated this in Genesis 12:8.