What are "Susim Meyuzanim"?
Rashi: They are horses whose Ever is hard (prepared for Bi'ah).
Radak: They fed them much at night, and they were satiated with their desire in the morning and joyfully neighed noisily. So [Yisrael] are adulterous at night with their neighbors' wives and fulfill their lust, and in the morning they go out happy, boasting of their evil.
What is the meaning of "Mashkim Hayu"?
Rashi: They rose early every morning [for Zenus].
Radak: Mashkim is a noun, like "vecha'Tal Mashkim Holech" (Hoshe'a 6:4) - early morning.
Why does it say "El Eshes Re'ehu"?
Rashi: They came to their friends' wives (for adultery).
Radak: This is like Ba'avur Eshes Re'ehu. (They exulted in the morning due to what they did with their friends' wives at night.)
What is "Yitzhalu"?
Rashi: This word is used for the joyful neighing of horses - "mi'Kol Mitzhalos Abirav" (8:16).
