Numbers - Chapter 7

In this chapter the tabernacle is set up ready for use, and each of the leaders of the Israelites presented their offerings to God.  Moses then hears God speak to him in the tabernacle.

"Now when Moses went into the tabernacle of meeting to speak with Him, he heard the voice of One speaking to him from above the mercy seat that was on the ark of the Testimony, from between the two cherubim; thus He spoke to him."

The mercy seat and the ark were behind the veil, so while Moses could hear God speak - he could not see him.  This voice of God will have come from the second person of the trinity, the one who is described by John as "the Word".