The popular expression "Seek and you shall find" is found in the Book of Matthew in the New Testament but clearly was inspired if not simply transposed from earlier Rabbinic and Torah texts such as this...
Matthew 7:7 Seek, and you shall find (v. 7): The idea of seeking after truth or wisdom is a favorite in Jewish wisdom: "I love those who love me; and those who diligently seek me will find me" (Prov. 8:17); "Then they will call on me, but I will not answer; they will seek me diligently, but they shall not find me" (Prov. 1:28, in reference to fools who normally do not seek wisdom); "Wisdom is radiant and unfading, and she is easily discerned by those who love her, and is found by those who seek her" (Wis. 6:12); "And you will seek Me and find Me, when you search for Me with all your heart" (Jer. 29:13): "If a man says to you, I have labored and not found,' do not believe him. If he says, I have labored and found, you may believe him.. all depends on the assistance of Heaven..." (b. Megillah 6b).
knock, and it shall be opened to you (v. 7):
See Song of Songs. 5:2 "I was asleep, but my heart was awake. A voice! My beloved was knocking:
Open to me, my sister, my darling, My dove, my perfect one!" And from rabbinic literature we have: "he knocked at the gates of mercy and they were opened to him" (b. Megillah
12b): "A man should always immerse himself in the Mishnayot, for if he knows, it will be opened to him" (Leo. Rab. 21.5 [on Lev. 16:3).
From The Bible Knowledge Background The Bible Knowledge Commentary Matthew-Luke · Volume 1 2003 Editor: Craig A. Evans