Genesis 49:28

All these are the twelve tribes of Israel
The twelve sons of Jacob before mentioned were heads of twelve tribes, who were afterwards seated, and had their part in the land of Canaan; there were indeed thirteen tribes, two springing from Joseph; but then the tribe of Levi had no part in the land of Canaan, which was divided into twelve parts; this shows that the above predictions respect not the persons of the patriarchs, but their tribes:

and this [is it] that their father spake unto them, and blessed them:
the above is the sum and substance of what he had delivered in his patriarchal benediction of them, a little before his death; and though some of them, as Reuben, Simeon, and Levi, may seem rather to be cursed than blessed, yet the greater part of them were clearly and manifestly blessed; and what he said by way of correction and rebuke to the others, might be blessed to them for their good; nor is it improbable, that after he had delivered out the above predictions, he might wish for and implore a blessing on them all; and certain it is, that they all had a part in the blessing of Abraham, Isaac, and Jacob, as it related to the land of Canaan:

everyone according to his blessing he blessed them;
according to the blessing which was appointed to them of God, and was in later times bestowed on them, Jacob under a spirit of prophecy was directed to bless them with, or to foretell what blessings should come upon them, and which accordingly did.