Does God Ever Refuse to Hear Prayers?

Most of us believe that when we “cry out” to God—that is, appeal to Him through prayer—He always hears those prayers. “Ask,” we read in Matthew 7:7, “and it will be given to you.” But what about Bible passages that suggest that sometimes God doesn’t listen to our prayers?

Consider Psalm 66, in which the author gives thanks that God answered his prayer, but suggests that God might not have done so in certain circumstances:

Come and hear, all you who fear God,
and I will tell what he has done for my soul.
I cried to him with my mouth,
and high praise was on my tongue.
If I had cherished iniquity in my heart,
the Lord would not have listened.
But truly God has listened;
he has attended to the voice of my prayer.

Blessed be God,
because he has not rejected my prayer
or removed his steadfast love from me! — Psalm 66:16-20 (ESV) (empahsis mine)