3 But seeing that is a great thing to know the mystery how He is David's Son and David's Lord: how one Person is both Man and God; how in the form of Man He is less than the Father, in the form of God equal with the Father; how again He says, on the one hand, “The Father is greater than I;” and on the other, “I and My Father are one;” seeing this is a great mystery, our conduct must be fashioned, that it may be comprehended. For to the unworthy is it closed up, it is opened to those who are meet for it.
It is not with stones, or clubs, or the fist, or the heel, that we knock unto the Lord. It is the life which knocks, it is to the life that it is opened. The seeking is with the heart, the asking is with the heart, the knocking is with the heart, the opening is to the heart. Now that heart which asks rightly, and knocks and seeks rightly, must be godly. Must first love God for His Own sake (for this is godliness); and not propose to itself any reward which it looks for from Him other than God Himself.
For than Him is there nothing better. And what precious thing can he ask of God, in whose sight God Himself is lightly esteemed? He gives earth, and you rejoice, you lover of the earth, who art yourself become earth. If when He gives earthly goods, you rejoice, how much more ought you to rejoice when He gives you Himself, who made heaven and earth? So then God must be loved for His own sake. For the Devil not knowing what was passing in the heart of holy Job, brought this as a great charge against him, saying, “Does Job worship God for His Own sake.”
Source: Sermons on Selected Lessons of the New Testament (New Advent)