1Jo 5:1-21. Who are the brethren especially to be loved (1Jo 4:21); Obedience, the test of love, easy through faith, which overcomes the world. Last portion of the epistle. The spirit’s witness to the believer’s spiritual life. Truths repeated at the close: Farewell warning.
Reason why our “brother” (1Jo 4:21) is entitled to such love, namely, because he is “born (begotten) of God”: so that if we want to show our love to God, we must show it to God’s visible representative.
Whosoever - Greek, “Everyone that.” He could not be our “Jesus” (God-Savior) unless He were “the Christ”; for He could not reveal the way of salvation, except He were a prophet: He could not work out that salvation, except He were a priest: He could not confer that salvation upon us, except He were a king: He could not be prophet, priest, and king, except He were the Christ [Pearson, Exposition of the Creed].
born - Translate, “begotten,” as in the latter part of the verse, the Greek being the same. Christ is the “only-begotten Son” by generation; we become begotten sons of God by regeneration and adoption.
every one that loveth him that begat - sincerely, not in mere profession (1Jo 4:20).
loveth him also that is begotten of him - namely, “his brethren” (1Jo 4:21).