Hi,

thanks for the email. I used to find these passages strange as well but the main issue we need to keep in front of us is whether someone is doing these things (circumcision, the vow etc) because they believe that it some kind of work necessary for salvation or whether it is done in order to gain an entrance to the people you are trying to save. Here Timothy was circumcised not because of any legal reason, but so that he could witness amongst the Jews. The bible knowledge commentary says concerning Acts 16:1-2

"This appears to contradict Paul’s thinking in Galatians 2:3-5 where he refused to let Titus be circumcised. The situations, however, were different. In Galatians 2 the issue was the method of justification; here it was a question of not giving offense (cf. 1 Cor. 9:19-23). The Jerusalem Council, of course, had determined circumcision was not necessary for salvation (Acts 15:10-11, 19). In Acts 16 Paul acted as he did for the sake of the ministry; it was a wise move."

So 1 Cor 9:19-23 is the key -

"Though I am free and belong to no man, I make myself a slave to everyone, to win as many as possible. 20 To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. 21 To those not having the law I became like one not having the law (though I am not free from God’s law but am under Christ’s law), so as to win those not having the law. 22 To the weak I became weak, to win the weak. I have become all things to all men so that by all possible means I might save some. 23 I do all this for the sake of the gospel, that I may share in its blessings. "

There is nothing wrong with circumcision or non-circumcision per se. It becomes wrong when the Jews thought they were righteous because of it. This is what Romans, Galatians etc is against.

As to Acts 21, apparently commentators are divided over whether this was a smart move by Paul or not. I can't really say... All I know is that again, this was not done for any legal reason. Paul saw it as an opportunity to get along side the Jews for the sake of being able to witness to them. As he said in Corinthians - "To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law."

Hope this helps,

All the best.