Matthew Henry Commentary Psalms 66:13-20

"I will come into thy house with burnt-offerings; I will pay thee my vows, Which my lips uttered, And my mouth spake, when I was in distress. I will offer unto thee burnt-offerings of fatlings, With the incense of rams; I will offer bullocks with goats. Selah Come, and hear, all ye that fear God, And I will declare what he hath done for my soul. I cried unto him with my mouth, And he was extolled with my tongue. If I regard iniquity in my heart, The Lord will not hear: But verily God hath heard; He hath attended to the voice of my prayer. Blessed be God, Who hath not turned away my prayer, Nor his lovingkindness from me." — Psalms 66:13-20 (ASV)

We should declare to those who fear God what he has done for our souls, and how he has heard and answered our prayers, inviting them to join us in prayer and praise. This will lead to our mutual comfort and to the glory of God.

However, we cannot share these spiritual privileges if we retain the love of sin in our hearts, even if we refrain from the gross practice. Sin, regarded in the heart, will spoil the comfort and success of prayer, for the sacrifice of the wicked is an abomination of the Lord.

But if the feeling of sin in the heart creates desires to be rid of it, and if that feeling is like the presence of someone urging a demand we know we must not—and indeed cannot—comply with, this is an argument for sincerity. And when we pray in simplicity and godly sincerity, our prayers will be answered. This will stir gratitude to him who has not turned away our prayer nor his mercy from us.

It was not prayer that brought about the deliverance, but his mercy that sent it. That mercy is the foundation of our hopes and the fountain of our comforts, and it should be the subject of our praises.