Deuteronomy 31:2

2And he said unto them, I am an hundred and twenty years old. Although Moses had been often proudly and disdainfully rejected, it could not but be the case, nevertheless, that his departure would both awaken the deepest sorrow, and inspire them with much alarm. By setting before them his age, therefore, he consoles their anxiety, and mitigates their grief; and also, by another reason, he represses their lamentations, i.e., that God had fixed his term of life. He adduces it, then, as an alleviation, because both his death was more than mature, and he was no longer fitted in his extreme old age for enduring fatigue. Here, however, the question arises, why he should say that he was failing, and broken in strength, when we shall see a little further on that he retained his senses in their rigor even until his death? But the reply is obvious, that he would not have been useless in his old age, because his eyes were dim or his members tremulous, but because his age no longer allowed him to perform his usual duties. For he had been marvelously and preternaturally preserved up to that time; but, since he had now arrived at the end of his course, it was necessary that he should suddenly sink, and be deprived of his faculties.

“To go out, and come in,” is equivalent to performing the functions of life: thus it is said in the Psalm, “Thou has known my going out and coming in.” (231) (Psalms 121:8.) And in this sense David is said to have gone out and come in, when he performed the duty intrusted to him by Saul. (1 Samuel 18:5.)

In the latter clause, where he refers to his exclusion from the land of Canaan, and his being prevented from entering it, he indirectly rebukes the people, for whose offense God had been wroth with himself and Aaron. Thus by this tacit reproof the Israelites were admonished to bear patiently the penalty of their ingratitude. At the same time., as he shows himself to be submissive to the divine decree, he bids them also acquiesce in it.