3 Him would Paul have go forth with him, and took him and circumcised him on account of the Jews who were in those places, for they all knew his father that he was a Greek. v.3 Timothy Circumcised. 

The reason why Paul had Timothy circumcised and not Titus is given to us; "because of the Jews which were in those quarters: for they knew all that his father was a Greek" (Acts 16:3). The issue with Timothy was that one parent was Jewish and the other Gentile, and so it would raise distracting questions about his ethnicity among the Jews. Paul used his Christian liberty, so that "unto the Jews I became as a Jew, that I might gain the Jews; to them that are under the law, as under the law, that I might gain them that are under the law" (1 Cor. 9:20). Paul did not compromise his principles with Timothy, but had rather used his Christian liberty to bring an end to any distraction over the issue. In Acts 15 it was a false teaching coming in among believers that circumcision was required for salvation. In Acts 16 it was to remove confusion among unbelievers whom Paul was trying to reach with the gospel. What the Jews wanted was to reject Timothy because of his mixed background, so Paul had him circumcised! The case of Titus was different (Gal. 2:3). Both the parents of Titus were Gentiles, and therefore he did not pose the same issue. In fact, the circumstances of him being a Gentile and uncircumcised is connected with why the Lord revealed to Paul that he should take Titus with him to the Jerusalem council. Titus was not compelled to take up with Jewish ceremony. To do so would be a compromise of principles! This makes Paul's position very clear.

 

9 And a vision appeared to Paul in the night: There was a certain Macedonian man, standing and beseeching him, and saying, Pass over into Macedonia and help us. 10 And when he had seen the vision, immediately we sought to go forth to Macedonia, concluding that the Lord had called us to announce to them the glad tidings. vv.9-10 Called to Macedonia. The gospel would now enter Europe for the first time!

11 Having sailed therefore away from Troas, we went in a straight course to Samothracia, and on the morrow to Neapolis, 12 and thence to Philippi, which is the first city of that part of Macedonia, a colony. And we were staying in that city certain days. 13 And on the sabbath day we went outside the gate by the river, where it was the custom for prayer to be, and we sat down and spoke to the women who had assembled. vv.11-13 By the River. Why were these Jews assembled by the river for prayer? Perhaps there was no synagogue in Philippi as it was a Roman colony.

 

26 And suddenly there was a great earthquake, so that the foundations of the prison shook, and all the doors were immediately opened, and the bonds of all loosed. 27 And the jailor being awakened out of his sleep, and seeing the doors of the prison opened, having drawn a sword was going to kill himself, thinking the prisoners had fled. 28 But Paul called out with a loud voice, saying, Do thyself no harm, for we are all here. 29 And having asked for lights, he rushed in, and, trembling, fell down before Paul and Silas. 30 And leading them out said, Sirs, what must I do that I may be saved? 31 And they said, Believe on the Lord Jesus and thou shalt be saved, thou and thy house. v.31

In scripture there is a difference between "believing", "believing in", and "believing on". If you "believe" someone, you accept what they say as truth. If you "believe in" someone, you have confidence in their character; i.e. it has to do with who they are, although it also includes that they are honest. If you "believe on" someone, they become an object for your faith, and this also includes both confidence in their character and in their words, but goes far higher.