Charles Ellicott Commentary Psalms 106:33

"Because they were rebellious against his spirit, And he spake unadvisedly with his lips." — Psalms 106:33 (ASV)

They provoked his spirit. —The natural interpretation is to understand this as referring to Moses’ spirit. The Septuagint and Vulgate translate it as, “they embittered his spirit.” However, the usage of the phrase favors referring the words to the people’s temper towards God: “they rebelled against His spirit.”

Spoke unadvisedly. —Compare the same verb with the same addition, “with the lips,” in Leviticus 5:4. This interpretation of Moses’ fault is partial. A comparison of all the historical narratives shows that it was for a momentary lapse into the people's despairing spirit, rather than for addressing them as rebels, that Moses was excluded from the Promised Land.