Rashi on Exodus 13:21/רש"י על שמות י״ג:כ״א

1לנחתם הדרך TO GUIDE THEM IN THE WAY — It (the ל of לנחתם) is punctuated with Patach, because it (the word) is like לְהַנְחוֹתָם (being a contracted form of this); similar is, (Deuteronomy 1:33) “לַרְאֹתְכֶם the way in which ye shall go”, which is the same as לְהַרְאֹתְכֶם to show you. Thus, too, here: לנחתם means as much as להנחותם to make them be guided i. e. by means of an agent. And who was this agent? The pillar of cloud — and the Holy One, blessed be He, in His glory (Himself) led it before them. Nevertheless He Himself did not act as their immediate guide, but He provided the pillar of cloud that they might be guided by means of it, for, as a matter of fact, as the Scriptural account shows, it was by means of the pillar of cloud that they set forth on their journeys. The pillar of cloud was not for giving light to them but to show them the way.