2 Kings 2:10

He said, Thou hast asked a hard thing A rare and singular blessing, which I cannot promise thee; which God only can give, and which he gives only when and to whom he pleases. Nevertheless, if thou see me, &c. Mark, this is a sign whether thou shalt obtain what thou desirest or not. This sign he proposed, not without the direction of God's Spirit, that hereby he might engage him more earnestly to wait, and more fervently to pray for this mercy.