וְהִנֵּ֣ה מִן־הַיְאֹ֗ר עֹלֹת֙ שֶׁ֣בַע פָּר֔וֹת יְפ֥וֹת מַרְאֶ֖ה וּבְרִיאֹ֣ת בָּשָׂ֑ר וַתִּרְעֶ֖ינָה בָּאָֽחוּ׃
И вот, вышли из реки семь коров, благодатных и толстых; и они питались тростниковой травой.
Rashi
יפות מראה BEAUTIFUL TO THE SIGHT — This was an indication of a period of plenty, when people show themselves well-disposed one to another, for no-one then envies another person’s prosperity (cf. Genesis Rabbah 89:4).
Chizkuni
מן היאור עולות, “rising up from the river Nile;” they had first descended to its banks to drink its waters.
Da'at Zekenim
והנה מן היאור, “and lo, out of the River (Nile)” seeing that famine and satiation have their origin in water, (irrigation or lack thereof of the earth) this was the symbol shown Pharaoh in his dream. (B’reshit Rabbah 89,4)