He left: Good News Translation and Die Bibel im heutigen Deutsch identify he as Jesus, since this verse opens a new section in the Gospel.
Left the crowds may be “went away from where the crowd was” or “left that place where the crowds were.”
Into the house (Good News Translation “indoors”) translates a Greek construction which may mean “in his house” (New American Bible “he went home”). The house referred to is the one in Capernaum (see 8.14; 9.10).
It may not be possible to say he went into the house without indicating first where he went, as in “He left the crowds and went to his house. He went in, and….”
It will be difficult to say the house in many languages unless it is clear which house is being referred to. Thus “his house” or “the house where he was staying” may be necessary.
And is simply a word to show the continuity of the story.
His disciples came to him implies that they had gone into the house with Jesus, and it may be necessary to indicate this explicitly in translation; for example, “When Jesus and his disciples had left the crowd and had gone indoors, his disciples came to him…” or “Jesus left the crowd and went indoors. His disciples went with him, and when they were inside alone, they came to him and said….”
Came may have to be “went.”
Explain (so also Die Bibel im heutigen Deutsch, New Jerusalem Bible, New English Bible) is translated “Tell … what … means” by Good News Translation. Elsewhere in the New Testament this verb is found only in 18.31.
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 .
