en_tn/gen/24/01.md

old, well advanced in years

The phrases "old" and "well advanced in years" mean the same thing. The two of them together emphasize that Abraham was "very old." (See: rc://en/ta/man/translate/figs-doublet)

Put your hand under my thigh

Abraham was about to ask the servant to swear to do something. Putting his hand under Abraham's thigh would show that he would certainly do what he would swear to do.

and I will make you swear

This can be expressed as a command: "and swear."

swear by Yahweh

This can be translated as "promise me in the name of Yahweh" or "promise me with God as your witness."

the God of heaven and the God of the earth

"the God of heaven and earth" or "the God of everything in heaven and earth" (See: rc://en/ta/man/translate/figs-merism )

from the daughters of the Canaanites, among whom I dwell

"from these Canaanites that we live among"

but you will go

This can be translated as a command: "Swear that you will go" or "But go."

my relatives

"my family"