Verses 23 and 24 form the conclusion of the second part of the Letter and briefly summarize its main points.

This is his commandment, or ‘what he (that is, God) commands is (this),’ ‘the one thing he/God commands us to do is (this).’

The demonstrative points forward to, and is explained by, the that clause. The singular form of the noun contrasts with the preceding plural and shows that this one commandment comprises all possible individual and partial commandments. For a similar shift from plural to singular, compare 2.3-4 with 2.8.

We should believe in the name of his Son Jesus Christ: this is a formula that briefly states a basic article of faith. The aorist tense shows that the reference is to the fact of believing as such.

† Believe: used with a nonpersonal goal this Greek verb means that one gives credence to a report heard or a fact perceived, accepting and acknowledging it as true and effective. It is used in this Letter with a direct object (4.16), a Greek preposition meaning “toward” (5.10c), or a “that” clause (5.1, 5).

With a personal goal the verb means that one gives credence to a person and accepts that he is speaking the truth (4.1). With Christ as goal “to believe (in)” means that one trusts Christ’s power to help, and that one is convinced of his existence and nearness, and of the truth of his words and revelations (3.23; 5.10a, 13). The verb is also used with God as goal (5.10b).

As has been pointed out in A Translator’s Handbook on the Gospel of Mark on 1.15, such English expressions as “to believe a report,” “to believe a person,” and “to believe in a person” often require quite different renderings. Many of these are figurative or descriptive phrases, mentioning various relationships or emotional centers.

In the sense the verb has here, some languages render it by such idioms as ‘to follow close after,’ namely, after one’s guide, ‘to offer one’s head to,’ ‘to lean (the heart) on,’ ‘to hang on to with the heart,’ ‘to join God’s/Christ’s word to the body,’ ‘to catch in the mind,’ ‘to put truth in.’ Other languages have a specific, nonfigurative term, or a combination of terms; for example, ‘to obey-believe,’ ‘to trust believing’; and in some cases ‘to believe’ and ‘to obey’ are rendered by the same term.

† Name (also in 5.13) in the Bible is frequently not only the distinctive designation of a person but stands also for his character and authority, almost for that person himself and all he is and does. This use of the term is not foreign to some receptor languages, and it seems to have been assimilated without much difficulty in others.

There are languages, however, where a literal rendering will not do in a context like this. In such cases the name of is often left untranslated. This is decidedly better than to press a corresponding phrase into the translation in a way that is not idiomatic, or does not bring out the intention of the original. For his Son Jesus Christ see comments on 1.3.

For to love one another, see comments on 3.11. The present tense has durative force.

Just as he has commanded us is in the Greek literally “just as he gave commandment to us.” This clause resembles 2 John 4, but there the subject of the clause is not he who gave the commandment, or who commanded, but those who received the commandment, or were commanded. Another possible rendering of the Greek clause is ‘in accordance with the commandment he gave us.’ Since in all other passages the term “commandment” is used of something which God commands (compare comments on 2.3), the pronoun probably refers to God. Then the clause takes up again the initial clause of verse 23, and together the two clauses form a figure of inclusion. This is a figure which is characteristic for John’s style in this Letter, compare comments on 2.18.

Several commentators and translators, however, take the commandment as being given by Jesus. This, though possible and even attractive, seems to be less probable. It would be contrary to the author’s usage in this Letter.

Quoted with permission from Haas, C., de Jonge, M. and Swellengrebel, J.L. A Handbook on The First Letter of John. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .