John Gill Commentary Psalms 136:16

"To him that led his people through the wilderness; For his lovingkindness [endureth] for ever:" — Psalms 136:16 (ASV)

To him which led his people through the wilderness
Where there was no path. This the Lord did by going before them in a pillar of cloud by day, and in a pillar of fire by night, to show them the way in which they should go, (Exodus 13:21Exodus 13:22) ; see (Psalms 78:14) ;

for his mercy [endureth] for ever ;
among the manifold mercies of God, shown to Israel in the wilderness, this is one taken notice of by Nehemiah, (Nehemiah 9:19) ; that the pillar of cloud and fire, to direct them, never departed from them while in it: and this act of "leading" them not only includes the guidance of them in the way, but the provision made for them; of water out of the rock, and of manna that fell about their tents every day; and of flesh and feathered fowl, like dust, so that they wanted nothing; and also the protection of them from their enemies: all which were proofs of his constant care over them, and continual mercy to them; see (Psalms 78:15Psalms 78:16Psalms 78:24Psalms 78:25Psalms 78:27) .