The apostles obeyed is literally “when they heard,” but “to hear” in this context obviously means “to obey.” In translating they entered … started teaching the Good News Translation brings out the contrast between the Greek tenses; the second of these verbs is a Greek imperfect, and here probably indicates the beginning of an action. A goal of the verb obey is an angel, hence “obeyed the angel.”

The last part of verse 21 actually begins with a participle that has been rendered as a finite verb in a number of translations (see, for example, Revised Standard Version “came”; New English Bible “arrived”). It is possible, also, to take this participle as a Lukan stylistic device indicating a transition in the discourse, and so a redundant feature in English. The Good News Translation understands it as conveying no new information, and has taken it merely as a transition, which has been indicated by the introduction of a new paragraph.

“Those with him” is translated his companions (Good News Translation), “his colleagues” (New English Bible), “his supporters” (Jerusalem Bible), and “his allies” (Phillips). The expression itself is a rather loose term, and may mean any group sharing together in a common undertaking.

“The Council and all the council of elders of the sons of Israel” represents a literal translation of the Greek which has been rendered by the Good News Translation all the Jewish elders for a full meeting of the Council. It is generally assumed that the two terms used here by Luke (that is, “Council” and “council of the elders”) are synonyms, the latter term simply explaining the former. It is best either to translate as the Good News Translation has done, or else to translate something like “a meeting of the Council, that is, of the full Jewish senate” (see New English Bible, Barclay, Jerusalem Bible).

The Jewish elders simply identifies those persons who constituted the Council. In some societies these are the “advisers.” In other instances elders may be translated as “the old men” or “the wise men.”

The final clause of verse 21 is somewhat complex from the standpoint of participants and causal relationships. In some languages these must be made more explicit, for example, “they sent men (or officials) to the prison to tell the guards to bring the apostles to the Council.”

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on The Acts of the Apostles. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .