Albert Barnes Commentary Acts 21:19

"And when he had saluted them, he rehearsed one by one the things which God had wrought among the Gentiles through his ministry." — Acts 21:19 (ASV)

Had saluted them. With the usual tokens of respect and affection.

He declared particularly, etc. As an evidence that God had been with him. It is not improbable that there might have been some suspicion in regard to Paul among the disciples at Jerusalem, and he might have heard that they were prejudiced against him. This prejudice would be removed by his stating what had actually occurred under his ministry.