ASV: but whoso keepeth his word, in him verily hath the love of God been perfected. Hereby we know that we are in him:

BBE: But in every man who keeps his word, the love of God is made complete. By this we may be certain that we are in him:

DBY: but whoever keeps his word, in him verily the love of God is perfected. Hereby we know that we are in him.

KJV: But whoso keepeth his word, in him verily is the love of God perfected: hereby know we that we are in him.

WEY: But whoever obeys His Message, in him love for God has in very deed reached perfection. By this we can know that we are in Him.

WBS: But whoever keepeth his word, in him verily is the love of God perfected: by this we know that we are in him.

WEB: But whoever keeps his word, God's love has most certainly been perfected in him. This is how we know that we are in him:

YLT: and whoever may keep his word, truly in him the love of God hath been perfected; in this we know that in him we are.
