Rashi on Genesis 48:20/רש"י על בראשית מ״ח:כ׳

1בך יברך ישראל IN THEE SHALL ISRAEL BLESS — When one wishes to bless his sons he will bless them by reciting the formula with which they were blessed — a man will say to his son, “God make thee as Ephraim and as Manasseh.”

2וישם את אפרים AND HE PUT EPHRAIM etc. — i.e. in the blessing he bestowed upon them he put Ephraim’s name before that of Manasseh, so giving him precedence over his brother when the Israelites encamped and marched beneath their banners in the wilderness (cf. Numbers 2:18 and Numbers 10:22), and when at the dedication of the altar by the princes of the tribes each brought his gifts (cf. Numbers 7:48 Numbers 7:54). (see Genesis Rabbah 97:5).