Jamieson, Fausset and Brown on Matthew 7:8

8. For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened--Of course, it is presumed that he asks aright--that is, in faith--and with an honest purpose to make use of what he receives. "If any of you lack wisdom, let him ask of God. But let him ask in faith, nothing wavering (undecided whether to be altogether on the Lord's side). For he that wavereth is like a wave of the sea driven with the wind and tossed. For let not that man think that he shall receive any thing of the Lord" (Jas 1:5-7). Hence, "Ye ask, and receive not, because ye ask amiss, that ye may consume it upon your lusts" (Jas 4:3).