James
James 1:6WEB·traditional attribution

But let him ask in faith, without any doubting, for he who doubts is like a wave of the sea, driven by the wind and tossed.

Geneva Bible Notes Reformed

But let him ask in faith, nothing wavering. For he that wavereth is like a wave of the sea driven with the wind and tossed. (f) Why then, what need is there of another mediator or priest? (6) A digression or going aside from his matter, as compared to prayers which are conceived with a doubting mind, but we have a trustworthy promise from God...

John Gill Reformed Baptist

But let him ask in faith,.... Not only in the faith of the divine Being that God is; but in the faith of the promises he has made; and in the faith of his power and faithfulness to perform them; and in the faith of this, that whatever is asked, according to the will of God, and is for his glory, and his people's good, shall be given.

Jamieson-Fausset-Brown Reformed

ask in faith--that is, the persuasion that God can and will give. James begins and ends with faith. In the middle of the Epistle he removes the hindrances to faith and shows its true character [BENGEL]. wavering--between belief and unbelief. Compare the case of the Israelites, who seemed to partly believe in God's power, but leaned more to unbelief by "limiting" it.