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, 2Ki_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.