Exegesis:

pas gar ho aitōn lambanei ‘for everyone who asks receives.’ A solemn and emphatic assurance, corresponding with the first clause of v. 9. Its nature is still further enhanced by pas and by the present tense of lambanei.

ho zētōn heuriskei ‘he who seeks finds,’ without pas and hence less emphatic than the preceding clause.

tō krouonti anoigetai ‘to him who knocks (the door) is opened.’

Translation:

Cf. on v. 9; objects, if required, can usually be fewer and less explicit because of the parallelism between the two verses.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.