Numbers 12:1 (BSB)

Then Miriam and Aaron criticized Moses because of the Cushite woman he had married, for he had taken a Cushite wife.

From Numbers 12. Also in the ESV.

Commentary on Numbers 12:1

• John Calvin (Reformed), Calvin's Commentaries on Numbers 12:1: 1. And Miriam and Aaron spoke against Moses. This relation is especially worthy of observation for many reasons. If Aaron and Miriam had always quietly and cordially supported the honor of their brother, and had not been carried away by perverse and ungodly jealousy, their harmony, however holy it was, would have been perverted by the injustice of many, and alleged against them as a deceitful and insidious conspiracy.
• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Numbers 12:1-3: Here is, I. The unbecoming passion of Aaron and Miriam: they spoke against Moses, Num 12:1. If Moses, that received so much honour from God, yet received so many slights and affronts from men, shall any of us think such trials either strange or hard, and be either provoked or discouraged by them? But who would have thought that disturbance should be created to Moses, 1.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Numbers 12:1: And Miriam and Aaron spoke against Moses,.... Miriam is first mentioned, because she was first in the transgression, and so was only punished; Aaron was drawn into the sin by her, and he acknowledged his fault, and was forgiven: it must be a great trial to Moses, not only to be spoken against by the people, as he often was, but by his near relations...
• Geneva Bible Notes (Reformed), Geneva Bible Study Notes on Numbers 12:1: And Miriam and Aaron spake against Moses because of the Ethiopian woman whom he had married: for he had married an Ethiopian woman. (a) Zipporah, Moses' wife, was a Midianite, and because Midian bordered on Ethiopia, it is sometimes referred to in the scriptures by this name.