Rashi on Deuteronomy 33:1/רש"י על דברים ל״ג:א׳

1וזאת הברכה … לפני מותו AND THIS IS THE BLESSING [WHEREWITH MOSES … BLESSED THE CHILDREN OF ISRAEL] BEFORE HIS DEATH — i.e., quite near to his death. “For” said he, “if not now, when?” (Sifrei Devarim 342:7).