Matthew Poole and continuators on Genesis 49:28

28 All these are the twelve tribes of Israel, and this is it that their father spake unto them, and blessed them: every one according to his blessing he blessed them.

(i. e.) The Heads and Parents of the Twelve Tribes. A Metonymy of the effect. The Tribes are generally accounted Twelve though they were Thirteen, because the Land was divided onely into Twelve parts, Levi having no distinct part of his own.

(i. e.) According to that blessing which God in his purpose had allotted to each of them, which also he manifested unto Iacob by his Spirit. Object. There is no blessing here given to Reuben, Simeon and Levi, but rather a curse, how then is he said to bless every one of them! Answ. He blessed them all implicitly and really, though not expresly or in words, because he gave each of them a part in Canaan; and his taking away from Reuben onely the right of the first-born plainly supposeth that he left him his single portion and inheritance. And he might well be said to bless them all, because he left them all an interest in Gods Covenant, one article whereof, was the giving of Canaan or part of Canaan to them, and this was an earnest of the other branches or articles of it. Though it is probable he also added some short blessing or prayer to God for his blessing upon them all.