Heubner:—To know Christ is to know, experience and delight in Him as our Friend and Saviour, and to enjoy His grace and fellowship. The mark of it is the keeping of His commandments, vital, active Christianity. Works are not the ground of justification, but a mark to ourselves, whether justifying faith is in us, and whether we are justified; because Christ when He gives Himself to us, never gives Himself half but entire; to whom He becomes justification, to them He also becomes sanctification. 

Lange, 1, 2, 3, John, 57