en_tn/gen/15/04.md

Then, behold

The word "behold" emphasizes the fact that the word of Yahweh came to Abraham again.

the word of Yahweh came to him, saying, "This

The idiom "The word of Yahweh came to" is used to introduce a special message from God. See how you translated this idiom in Genesis 15:1. AT: "Yahweh gave him a message. He said, 'This" or "Yahweh spoke this message to him: 'This" (See: rc://en/ta/man/translate/figs-idiom)

This man

This refers to Eliezer of Damascus.

the one who will come from your own body

"the one that you will father" or "your very own son." Abram's own son would become his heir.