Acts 21:4

‘And having found the disciples, we tarried there seven days, and these said to Paul through the Spirit, that he should not set foot in Jerusalem.'

There at Tyre they spent the customary ‘seven days' and it was here that Luke mentions for the first time the prophecies concerning what was to happen to Paul. But that these had been happening with alarming frequency we have already learned from Acts 20:23. Here certain disciples who were prophets said to Paul through the Spirit that he should not set foot in Jerusalem. This must mean either that the Spirit had in prophecy warned them of what was to happen, and they then gave him the message that he should not set foot in Jerusalem, or that the message was given as a warning so that the churches would be aware of the situation, even though the Spirit knew that he would set foot in Jerusalem under His compulsion (Acts 19:21; Acts 20:22).

The seven days may have been the time necessary for the unloading of their cargo and the taking aboard of a new cargo. Either way it give opportunity for fellowship with, and teaching to, the Christians at Tyre.