Peter asks this question to rebuke Sapphira. Alternate translation: "You should not have agreed together to test the Spirit of the Lord!" (See: [[rc://en/ta/man/jit/figs-rquestion]])
The word "Look" is an idiom for "Pay attention!" Peter is probably telling Sapphira to pay attention to the sound of the men's footsteps, which indicate that they are about to enter the building, not to look at their feet. Here the phrase "the feet" can be either a synecdoche for the men whose feet they are or a metonym for the sound that they make. Alternate translation: "Pay attention! The men" or "Listen! The footsteps of the men" (See: [[rc://en/ta/man/jit/idiom]] and [[rc://en/ta/man/jit/figs-synecdoche]] and [[rc://en/ta/man/jit/figs-metonymy]])