Adam Clarke on Nehemiah 9:19

The pillar of the cloud departed not from them - מעליהם mealeyhem, "from over them." I have already had occasion to observe that this miraculous cloud, the symbol of the Divine presence, assumed three different positions while accompanying the Israelitish camp:

1. As a cloud in the form of a pillar, it went before them when they journey, to point out their way in the wilderness.

2. As a pillar of fire, it continued with them during the night, to give them light, and be a rallying point for the whole camp in the night season.

3. As an extended cloud, it hovered over them in their encampments, to refresh them with its dews, and to keep them from the ardours of the sun.