A.T. Robertson Commentary 1 John 4:12

"No man hath beheld God at any time: if we love one another, God abideth in us, and his love is perfected in us:" — 1 John 4:12 (ASV)

No one hath beheld God at any time (θεον ουδεις πωποτε τεθεατα). Perfect middle indicative of θεαομα (John 1:14). Almost the very words of Joh 1:18 θεον ουδεις πωποτε εωρακεν (instead of τεθεατα).

If we love one another (εαν αγαπωμεν αλληλους). Third-class condition with εαν and the present active subjunctive, "if we keep on loving one another."

God abideth in us (ο θεος εν ημιν μενε). Else we cannot go on loving one another.

His love (η αγαπη αυτου). More than merely subjective or objective (2:5; 4:9). "Mutual love is a sign of the indwelling of God in men" (Brooke).

Is perfected (τετελειωμενη εστιν). Periphrastic (see usual form τετελειωτα in 2:5; 4:17) perfect passive indicative of τελειοω (cf. 1:4). See verse 18 for "perfect love."