He shall not return into ... Egypt - namely, to seek help against Assyria (compare Hos 7:11), as Israel lately had done (2Ki 17:4), after having revolted from Assyria, to whom they had been tributary from the times of Menahem (2Ki 15:19). In a figurative sense, “he shall return to Egypt” (Hos 9:3), that is, to Egypt-like bondage; also many Jewish fugitives were literally to return to Egypt, when the Holy Land was to be in Assyrian and Chaldean hands.
Assyrian shall be his king - instead of having kings of their own, and Egypt as their auxiliary.
because they refused to return - just retribution. They would not return (spiritually) to God, therefore they shall not return (corporally) to Egypt, the object of their desire.