Genesis 15:8

Whereby shall I know that I shall inherit it?— "Whereby shall I be ascertained, that my posterity shall possess this land, in right of that inheritance which thou hast given to me?" For the higher confirmation, of his faith, he asks some miraculous sign and pledge of the certainty of an event, of which he himself was not personally to partake. It is also probable from Genesis 15:13, that Abram's request means no more, than that God would vouchsafe to let him know, when the promise should be accomplished, and what signs should foreshew the event to himself or his posterity, as near at hand: in the same sense as the disciples say to Christ, Lord, when shall these things be, and what shall be the sign of thy coming? Matthew 24:3.