Surah 20. Ta-Ha, Ayah 12

Whereas some commentators assume that the word tuwan (or tawa) is the name of the "hallowed valley", Zamakhshari explains it, more convincingly, as meaning "twice" (from tawan or tiwan, "twice done")-i.e., "twice-hallowed" - apparently because God's voice was heard in it and because Moses was raised there to prophethood.

The shoes are to be put off as a mark of respect. Moses was now to put away his mere worldly interests, he having been chosen by Allah, the Most High.

This was the valley just below Mount Sinai, where subsequently he was to receive the Torah.