Or HaChaim on Deuteronomy 34:4/אור החיים על דברים ל״ד:ד׳

1 לאמור לזרעך אתננה, to say: "to your descendants I will give it." The reason the Torah had to write the word לאמור "to say" at this juncture, was that as of now G'd had not given this information to the patriarchs. [In connection with a statement that the dead communicate with one another, Ed.], our sages in Berachot 18 claim that G'd ordered Moses to tell the three patriarchs (after his death) that He had already discharged the oath He had sworn to them to give the land to their descendants. Perhaps the reason G'd wanted Moses to tell the patriarchs [instead of telling them Himself, Ed.] may have been so that Moses would make sure that the patriarchs would appreciate that G'd was able to keep His promise to them only after having overcome many difficulties and setbacks en route.

2ושמה לא תעבור, "but you yourself will not cross there." Perhaps the reason this is repeated at this point is that G'd wanted to tell Moses that he did not need to enter the gate to heaven by first having set foot in the land of Israel. The Zohar volume one page 81 says that all the souls ascend to heaven by way of ארץ ישראל. Seeing that Moses' soul was being gathered up by G'd personally, and that G'd immediately deposited it in the Celestial Regions, there was no need for his soul to travel via ארץ ישראל in order to achieve its objective. The words וימת שם משה mean that where Moses died his soul ascended to heaven immediately.