Exodus 4:10

Of tongue, being impressed with awe, at the divine presence. He feared, therefore, that he should not be able to deliver himself intelligently at the court of Pharao, and might rather excite the disgust of that haughty tyrant. (Haydock) --- He had been 40 years absent in the land of Madian, and might have forgotten both the Egyptian and Hebrew languages in some degree; in which sense slowness or heaviness of tongue is taken, (Ezechiel iii. 5.) to express an unknown language. (Calmet) --- God was thus pleased to shew, that all the glory arising from this enterprize belonged to himself; and he thus also gave occasion to Moses to humble himself, while he wrought miracles. (Menochius)