Charles Ellicott Commentary Acts 21:5

"And when it came to pass that we had accomplished the days, we departed and went on our journey; and they all, with wives and children, brought us on our way till we were out of the city: and kneeling down on the beach, we prayed, and bade each other farewell;" — Acts 21:5 (ASV)

We departed, and went our way.—Literally, and were going on our way, the tense bringing before us something like a procession making its way from the city to the shore.

We kneeled down on the shore, and prayed.—The choice of the place was in itself natural enough. It was the spot where the two groups of friends were to part, and it was removed from the stir and bustle of the city. We may add that this choice aligned with the common Jewish practice of using the banks of rivers or the seashore as a place of prayer. The beach of Tyre became for the time a proseuchè. (See Note on Acts 16:13.)

It seems implied from the use of the plural that, in this instance, St. Paul was not the only spokesman for the prayers, but that others also (probably St. Luke himself and the leading members of the Church of Tyre) joined in reciprocal intercession.