What does Genesis 49:25 mean?

When delivering prophecies about his son's descendants (Genesis 49:1–2), Jacob has been brief, in most cases. Other than Judah, most of his twelve sons have been given a short prediction. That changes with Jacob's oracle about Joseph (Genesis 49:22–24). In this extensive expression, Jacob speaks about the God who will protect and deliver Joseph's people. This explains God in personal terms. In the previous verse, Jacob named Him "the Mighty One of Jacob," "the Shepherd," and "the Stone of Israel."

Now, nearing death (Genesis 48:1), Jacob tells Joseph that the Lord is "the God of your father who will help you." For all the struggles of Jacob's life (Genesis 47:9), it would have been deeply comforting to remember that God had made good on all His promises. He knows that God had been faithful to him all his days. Now he understood that his God would be ready and able to help his sons and their offspring long after he was gone.

Jacob refers to God as "the Almighty," using the Hebrew word Sad'day. This title is directly associated with God, often phrased as ēl Sad'day, transliterated into English as El Shaddai. The book of Genesis often associates this name of God with blessings. Jacob certainly understands that El Shaddai has blessed him repeatedly during his life. Now he prays and prophesies that the Lord God will bless Joseph and his offspring.

In fact, God Almighty will supernaturally bless Joseph's descendants in every way humans can be blessed. They will be blessed from above, likely meaning rain in season for the crops, from below, with water from wells and streams, and from breasts and wombs, describing many and thriving children. The God who has blessed Jacob will continue to bless Jacob's children for generations to come, through the prosperity of the tribes of Ephraim and Manasseh.