Commentaries:
Robertson's Word Pictures (NT)
For he wist not what to answer (ou gar hdei ti apokriqh). Deliberative subjunctive retained in indirect question. But why did Peter say anything? Luke says that he spoke, "not knowing what he said," as an excuse for the inappropriateness of his remarks. Perhaps Peter felt embarrassed at having been asleep (Luke 9:32) and the feast of tabernacles or booths (skhnai) was near. See on Matthew 17:4. Peter and the others apparently had not heard the talk of Moses and Elijah with Jesus about his decease (ecodon, exodus, departure) and little knew the special comfort that Jesus had found in this understanding of the great approaching tragedy concerning which Peter had shown absolute stupidity (Mark 8:32 f.) so recently. See on Matthew 17:5 about the overshadowing and the voice.
Other Robertson's Word Pictures (NT) entries containing Mark 9:6:
Mark 14:40
Luke 9:33
Hebrews 12:21
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