James 4:2:

Ye lust, and have not: ye kill, and desire to have, and cannot obtain: ye fight and war, yet ye have not, because ye ask not.

See also:

We Hold the Keys
The Prayer of Nothing
What 1 John 1:9 Really Means
If God Wants People Healed, Why Doesn’t He Heal Them?
Objection: James Said to Say, “If the Lord Will, We Shall Live.”  This Proves That We Cannot Claim Long Life.
Objection: Sometimes God Says, “Yes,” Sometimes He Says, “No,” and Sometimes He Says, “Wait” When You Ask for Healing