6 But when you ask, you must believe and not doubt, because the one who doubts is like a wave of the sea, blown and tossed by the wind.

Read James 1:6 Using Other Translations

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.
But let him ask in faith, with no doubting, for the one who doubts is like a wave of the sea that is driven and tossed by the wind.
But when you ask him, be sure that your faith is in God alone. Do not waver, for a person with divided loyalty is as unsettled as a wave of the sea that is blown and tossed by the wind.