Luke 9:33

33 As Moses and Elijah were leaving him, Peter said to Jesus, "Teacher, it's good that we're here. Let's put up three tents--one for you, one for Moses, and one for Elijah." Peter didn't 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 appeared in heavenly glory and were discussing Jesus' approaching death and what he was about to fulfill in Jerusalem.

32 Peter and the men with him were sleeping soundly. When they woke up, they saw Jesus' glory and the two men standing with him.

33 As Moses and Elijah were leaving him, Peter said to Jesus, "Teacher, it's good that we're here. Let's put up three tents--one for you, one for Moses, and one for Elijah." Peter didn't know what he was saying.

34 While he was saying this, a cloud overshadowed them. They were frightened as they went into the cloud.

35 A voice came out of the cloud and said, "This is my Son, whom I have chosen. Listen to him!"