Genesis 15:8

Whereby shall I know? This request for a sign may be compared with the requests of Gideon (Judges 6:17, 36-40) and Hezekiah (2 Kings 20:8). Abram’s question was not a symptom of unbelief or doubt, but the expression of heartfelt longing to see the promises of God fulfilled. Later, Zacharias, in unbelief, asked for a sign (Luke 1:18, 20), but Mary put a similar question to the angel in faith, humbly yearning for further assurance (Luke 1:34, 35). God, who sees the heart and answers accordingly, recognized the right of his faithful servant Abram to seek for faith’s full assurance.