Peter put them all forth; Peter put them out, that he might pray the more earnestly, without distraction or interruption; thus Elisha shut the door to him when he prayed for the Shunammite's son, 2 Kings 4:33. Kneeled down; this his kneeling is mentioned, to recommend reverence in our praying unto God. And prayed: Peter, by his betaking himself unto prayer, would show, that he could do nothing by his own power, but it must come from above; and he had every mercy as much precariously, and by prayer, as any others.
Related Commentaries of Acts 9:40
Acts 9:40
40 But Peter put them all forth, and kneeled down, and prayed; and turning him to the body said, Tabitha, arise. And she opened her eyes: and when she saw Peter, she sat up.