Moses
Genesis 15:4ESV·traditional attribution

And behold, the word of the LORD came to him: “This man shall not be your heir; your very own son shall be your heir.”

John Calvin Reformed @genevareformer

4. This shall not be thine heir . We hence infer that God had approved the wish of Abram. Whence also follows the other point, that Abram had not been impelled by any carnal affection to offer up this prayer, but by a pious and holy desire of enjoying the benediction promised to him.

Matthew Henry Presbyterian @wholebiblehenry

We have here the assurance given to Abram of a numerous offspring which should descend from him, in which observe, I. Abram's repeated complaint, Gen 15:2, Gen 15:3. This was that which gave occasion to this promise. The great affliction that sat heavy upon Abram was the want of a child; and the complaint of this he here pours out before the Lord, and shows...

Commenting on Genesis 15:2-6

John Gill Reformed Baptist @doctorgill

And behold, the word of the Lord came unto him,.... Either having disappeared, and then came a second time, or he again spoke unto him: saying, this shall not be thine heir; this Eliezer, this servant of thine, as thou hast made him, or hast intended to make him, giving up all hopes of having issue by Sarai: but he that shall come forth out...