Or HaChaim on Genesis 49:25/אור החיים על בראשית מ״ט:כ״ה

1 מאל אביך ויעזרך, "From the G'd of your father who will continue to help you, etc." Jacob tells Joseph that his accomplishments are due to the G'd of Jacob; he even hints that Joseph drew on his father's merit so that he could have accomplished all that he did. Jacob prays that G'd should continue to help Joseph, ויעזרך. He adds ואת שדי, saying that yet another attribute (dimension) of G'd has assisted Joseph, the attribute that is particularly suited to the soul of Joseph, a mystical dimension familiar to students of the Kabbalah. It was this attribute which blessed and helped Joseph maintain his purity in a foreign land in the house of a pagan dignitary such as Potiphar.

2When Jacob spoke about ויעזרך..ויברכך, he may also have wanted to stress that G'd's help notwithstanding, Joseph deserved credit for his own efforts in resisting this temptation. G'd blessed him as if Joseph had accomplished all this by himself. The author refers to his commentary in this context on Psalms 37,33 where he elaborated on this theme.

3Jacob may also have based his blessing on the well known statement by our sages in Berachot 10 that when someone credits someone else with his own accomplishment, G'd may credit him with it instead, whereas if one claims that one's own merit accounts for one's good fortune, then G'd will teach one that it was only someone else's merit that resulted in that person's blessings. Jacob said that because Joseph credited his father's merit with assisting him at a critical juncture, G'd would credit Joseph himself with having mastered his temptation.

4Jacob may have expressed another message in his blessing of Joseph. Baba Batra 58 teaches that G'd does not perform miracles for people who will not remain righteous. Jacob therefore said that up to that point Joseph enjoyed G'd's blessings מאל אביך, because of his father's merit, whereas from now on ויעזרך G'd would assist him not to succumb to temptation in order to justify the miracles He had already performed for him. [I have not been able to find the source of this statement. Ed.]