Augustine of Hippo
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?
(ubi sup.) Having laid aside the metaphor, our Lord added an exhortation, and expressly urged us to ask, seek, and knock, until we receive what we are seeking. Hence he says, And I say unto you, Ask, and it shall be given you.