1 John 4:21 New English Translation

²¹And the commandment we have from him is this: that^[a] the one who loves God should love his fellow Christian^[b] too.

1 John 4:21 tn The ἵνα (hina) clause in 4:21 could be giving (1) the purpose or (2) the result of the commandment mentioned in the first half of the verse, but if it does, the author nowhere specifies what the commandment consists of. It makes better sense to understand this ἵνα clause as (3) epexegetical to the pronoun ταύτην (tautēn) at the beginning of 4:21 and thus explaining what the commandment consists of: “that the one who loves God should love his brother also.”
1 John 4:21 tn See note on the phrase “fellow Christian” in 2:9.

New English Translation (NET)