Whereby shall I know that I shall inherit it? — This did not proceed from distrust of God's power or promise, but he desired this, For the strengthening of his own faith. He believed, Genesis 15:6, but here he prays, Lord help me against my unbelief, Now, he believed, but he desired a sign, to be treasured up against an hour of temptation. For the ratifying of the promise to his posterity, that they also might believe it.
Related Commentaries of Genesis 15:8
Genesis 15:8
8 And he said, Lord GOD, whereby shall I know that I shall inherit it?