What does Exodus 13:21 mean?

God actively leads Israel on their journey out of Egypt (Exodus 13:17–18) using an impressive display. The Hebrew term 'ammud describes a column: a cylinder shape. God visibly appears to the nation covered by a cylinder of clouds (Exodus 33:20). Later descriptions strongly suggest the clouds and fire were part of a single column (Exodus 14:19–20, 24; 40:38). This display was visible during the day because of the clouds, and at night because of the "fire," which may have been lightning. Artist's depictions of these columns often resemble a tornado, though this passage does not use Hebrew words for a swirling stormy wind.

This guide was always there, never disappearing, as Israel traveled (Exodus 13:22). Having a constant guide, and light at night, helped Israel to travel quickly. This will become important, as the Egyptian army will soon chase them down (Exodus 14:5–8, 19). By then, the people will be on the seashore (Exodus 14:2). There, the pillar will move from leading Israel to guarding the exposed rear of their caravan (Exodus 14:19–20).