Teacher is the same noun of address used of Jesus in verses 16 and 24.

Which is the great commandment in the law? is a literal rendering of the Greek text, except that in Greek the verb is is unexpressed because it is not required by the rules of Greek grammar. In place of great, many languages will prefer the superlative form “greatest” (Good News Translation). Mark frames the question somewhat differently: “Which commandment is the first of all?” (12.28). But Matthew is concerned with the role of the Jewish Law for the Christian community, and this is what has determined the manner in which he introduces the question. Note also verse 38.

Great commandment can be rendered fairly literally in many languages, but in others “most important commandment” is more natural.

For comments on the law, see 5.17.

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .