And it came to pass, as they departed from him,.... That is, as Moses and Elias departed from Christ; or "when they began to depart", as the Syriac version renders it; or "would depart", as the Arabic and Persic versions; seemed desirous of going, or made some signal or other by which the disciples perceived they were about to go; for, as yet, they were not gone; Peter said unto Jesus, master, it is good for us to be here, let us make three tabernacles, one for thee, and one for Moses, and one for Elias; See Gill on Mat 17:4. not knowing what he said, nor "what to say", as Mark observes, being in a surprise, and not in a situation to consider and weigh things well, whether what he said was right and proper, or not; See Gill on Mat 17:4