Or HaChaim on Deuteronomy 31:27/אור החיים על דברים ל״א:כ״ז

1 הן בעודני חי עמכם, "Behold even while I am still alive amongst you, etc." This again reminds us of what the Talmud stated in Berachot 18 that the righteous are called alive even after their bodies have died. When Moses mentions the words: "here when I am still alive amongst you," he did not imply that he would soon die, but that he would live in a different region of the universe, one which could not be described as עמכם, "amongst you."

2The Torah writes היום, "today," i.e. Moses hinting that the "amongst you" he spoke of refers only to the balance of the day on which he was addressing them. The plain meaning of the verse is that the word היום means עד היום, "until today."

3The reason that Moses referred to the people's acts of rebellion in the past tense, i.e. הייתם, was in case they had already repented of their sins at that very hour. We have been taught in Kidushin 49 that if someone betrothes a woman on the understanding that he (the groom) is a totally righteous person, and we are aware that until very shortly prior to that moment he was a thoroughly wicked person, the lady in question has to consider herself as betrothed as we assume the groom had resolved to become a perfect בעל תשובה at the time he asked her to accept the token of her betrothal to him.