Rashi on Deuteronomy 33:13/רש"י על דברים ל״ג:י״ג

1מברכת ה' ארצו BLESSED OF THE LORD BE HIS LAND — It is a fact that there was in the inheritance of all the tribes no land so full of every good thing as Joseph's land (Sifrei Devarim 353:1).

2ממגד — this means dainties and sweet food.

3ומתהום [BLESSED OF THE LORD BE HIS LAND] BY THE DEEP — for the deep ascended and moistened it from below (תחת). — You will find that in the case of each tribe Moses' blessing corresponded in some way with Jacob's blessing (cf. for instance this verse with Joseph's blessing in Genesis 49:25).