Adam Clarke on Nehemiah 6:10

Who was shut up - Lived in a sequestered, solitary state; pretending to sanctity, and to close intercourse with God.

Let us meet together in the house of God - The meaning is, "Shut yourself up in the temple; appear to have taken sanctuary there, for in it alone can you find safety." This he said to discourage and disgrace him, and to ruin the people; for, had Nehemiah taken his advice, the people would have been without a leader, their enemies would have come upon them at once, and they would have been an easy prey. Besides, had Nehemiah done this, he would have been shut up in the temple, his government would have been declared at an end, and Sanballat would have assumed the reins.