Luke 9:33

33 And when they were preparing to depart from Him, Peter said to Jesus, "Rabbi, we are thankful to you that we are here. Let us put up three tents--one for you, one for Moses, and one for Elijah." He did not know what he was saying.

Luke 9:33 Meaning and Commentary

Luke 9:33

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 Matthew 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 Matthew 17:4)

Luke 9:33 In-Context

31 They came in glory, and kept speaking about His death, which He was so soon to undergo in Jerusalem.

32 Now Peter and the others were weighed down with sleep; but, keeping themselves awake all through, they saw His glory, and the two men standing with Him.

33 And when they were preparing to depart from Him, Peter said to Jesus, "Rabbi, we are thankful to you that we are here. Let us put up three tents--one for you, one for Moses, and one for Elijah." He did not know what he was saying.

34 But while he was thus speaking, there came a cloud which spread over them; and they were awe-struck when they had entered into the cloud.

35 Then there came a voice from within the cloud: "This is My Son, My Chosen One: listen to Him."