John Chrysostom
Catena Aurea · Lukasevangelium 11
And I say unto you, Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you. For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened. If a son shall ask bread of any of you that is a father, will he give him a stone? or if he ask a fish, will he for a fish give him a serpent? Or if he shall ask an egg, will he offer him a scorpion? If ye then, being evil, know how to give good gifts unto your children: how much more shall your heavenly Father give the Holy Spirit to them that ask him?
(Hom. 23. in Matt.) Now by asking, He means prayer, but by seeking, zeal and anxiety, as He adds, Seek, and ye shall find. For those things which are sought require great care. And this is particularly the case with God. For there are many things which block up our senses. As then we search for lost gold, so let us anxiously seek after God. He shews also, that though He does not forthwith open the gates, we must yet wait. Hence he adds, Knock, and it shall be opened unto you; for if you continue seeking, you shall surely receive. For this reason, and as the door shut makes you knock, therefore he did not at once consent that you might entreat.