Komentarz do Powtórzonego Prawa 1:5

הואיל means HE BEGAN, just as (Genesis 18:27) "Behold, now I have begun (הואלתי)" (cf. Sifrei Devarim 4:1).

בעבר הירדן בארץ מואב הואיל משה באר, seeing that they were no longer moving around all the time, for the encampment in the steppes near Moav was their last stop before crossing the Jordan. Now, seeing that Moses himself had already given up hope of personally crossing the river Jordan he began to explain the parts of the Torah concerning which he thought some doubts could arise after his death. He did this by starting with a reminder of the covenant concluded between Israel and G’d at Mount Chorev. (compare 5,2) לאמר, before beginning with reviewing portions of the Torah, Moses explained the reason for the need to do this as being that they were about to cross into what would become their homeland where many commandments of the Torah would apply for the first time. Seeing that he could not do this at the time when they actually applied already, he had to do this now before his death. While on the subject, Moses reminded the people how, indirectly, due to their sinful conduct he was now unable to cross the Jordan with them, and that as a result he wanted to make sure that they would not again become guilty of such sinful behaviour.