This entire verse requires a good deal of restructuring from the Greek because the verb phrase is divided, the first part coming at the beginning of the sentence and the last part at the very end, with the clause describing John Mark coming in between.

Either did not think it was right or “was not in favor of” (Jerusalem Bible) correctly translates the meaning of the verb that Luke has chosen to describe Paul’s attitude. The choice of a word for right should not imply moral rightness, in contrast with something which was morally wrong. It is simply a matter of whether it was a good thing to have John Mark go along with them.

The literal expression “to the work” is translated to the end of their mission inasmuch as “work” is used in several places in Acts as a specific term of reference for the Christian missionary effort (see 13.2; 14.26). Moreover, it is obvious that Paul meant that John Mark had left them and had not completed the mission that they had intended to undertake. In some languages the expression not stayed with them to the end of their mission may be rendered as “did not stay with them until they had completed their work” or “did not stay with them until they finished what they had started to do.”

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 .