Matthew 7:7. Ask, and it will be given you; seek, and you will find; knock, and it will be opened to you.  8. For every one who asks, receives, and he who seeks, finds, and to him who knocks it will be opened.  9. Or what man of you, if his son asks him for a loaf, will give him a stone? 10. Or if he asks for a fish, will give him a serpent? 11. If you, then, who are evil, know how to give good gifts to your children, how much more will your Father who is in heaven give good things to those who ask Him?

After teaching His disciples and instituting the office of the ministry, telling them what they are expected to preach and how they are to live, Christ, the Lord, now adds an admonition to prayer. By this He intends to teach them that, second only to the office of preaching, prayer is the chief work of a Christian and an inseparable part of the sermon. He also wants to indicate that because of all the temptations and hindrances we face, nothing is more necessary in Christendom than continual and unceasing prayer that God would give His grace and His Spirit to make the doctrine powerful and efficacious among us and among others. That is why, in the words we quoted from the prophet Zechariah (Zech. 12:10), God promised that He would pour out upon the Christians a Spirit of grace and of supplication. In these two items He summarizes all Christian existence. (Luther’s Works, v. 21, pages 228-229).