Or HaChaim on Numbers 12:8/אור החיים על במדבר י״ב:ח׳

1 ומדוע לא יראתם לדבר, "why were you not afraid to speak?, etc" G'd repeats once more that they themselves should have been able to figure out that since Moses was constantly performing commands of G'd and was used by G'd as His instrument, surely He would not have chosen him for such a function if he had been guilty of neglecting such a basic commandment as family life which Miriam and Aaron accused him of. G'd stressed not only the word עבדי, i.e. that He described Moses as His servant, but He added Moses' name to indicate that this man had been destined for greatness. How could they have suspected him! It is also possible that the word במשה indicates that Miriam and Aaron did say what they said in Moses' presence, adding insult to injury. We discussed this in connection with verse 1 in this chapter.