But the angel said to him, “Do not be afraid, Zacharias, for your prayer is heard; and your wife Elizabeth will bear you a son, and you shall call his name John. – Luke 1:13

“Thy prayer is heard.” I marvel at his faith that he should persevere in prayer for a boon which seemed, at his own and his wife’s age, to have been out of the course of nature, and beyond the domain of hope, but I marvel a great deal more that, when the answer came to that very prayer, Zacharias could not believe it. So full often is it with us; nothing would surprise some of us more than to receive an answer to some of our prayers. Though we believe in the efficacy of prayer, at times we believe so feebly that when the answer comes, as come it does, we are astounded and filled with amazement. We can scarcely think of it as a purpose of God, it seems rather to us like a happy coincidence. Surely this adds greatly to the sin of unbelief. If we have been asking for mercy without expecting it, and pleading promises while harbouring mistrust, every prayer we have offered has been only a repetition of our secret unbelief; and it is God’s faithfulness that brings our inconsistency to light.

I may be addressing some poor woman here who, in the depth of affliction, bodily suffering, and poverty, nevertheless rejoices in God with all her heart. But without a doubt, I am now speaking to many a man who is vexed with trifling cares, murmurs bitterly because of petty annoyances, and distrusts his God when clouds come over the sky so that he sees not his way. Shame on our unbelief. Think shame of yourselves because of it, I pray you. Never does it disgrace us more than when the weaklings of the Lord’s family put us to the blush by the simplicity and sincerity of their faith.  ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/3495.cfm