Albert Barnes on Acts 21:14

Would not be persuaded. To remain. He was resolved to go. We ceased. We ceased remonstrating with him, and urging him to remain.

The will of the Lord be done. They were now assured that it was the will of God that he should go. And they were now ready to submit to that will. This is an instance and an evidence of true piety. It was the expression of a wish, that whatever God might judge to be necessary for the advancement of his cause might take place, even though it should be attended with many trials. They commended their friend to the protection of God, confident that whatever should occur would be right. Compare Mt 6:10, 26:42.

(a) "will of the Lord" Mt 6:10, 27:42