Luke 9:33

33 As the men were leaving Jesus, Peter said to him, "Master, how good it is that we are here! We will make three tents, one for you, one for Moses, and one for Elijah." (He did not really 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 who appeared in heavenly glory and talked with Jesus about the way in which he would soon fulfill God's purpose by dying in Jerusalem.

32 Peter and his companions were sound asleep, but they woke up and saw Jesus' glory and the two men who were standing with him.

33 As the men were leaving Jesus, Peter said to him, "Master, how good it is that we are here! We will make three tents, one for you, one for Moses, and one for Elijah." (He did not really know what he was saying.)

34 While he was still speaking, a cloud appeared and covered them with its shadow; and the disciples were afraid as the cloud came over them.

35 A voice said from the cloud, "This is my Son, whom I have chosen - listen to him!"