Israel is referred to in Hos 5:9, Judah in Hos 5:10.
the day of rebuke - the day when I shall chastise him.
among the tribes of Israel have I made known - proving that the scene of Hosea’s labor was among the ten tribes.
that which shall surely be - namely, the coming judgment here foretold. It is no longer a conditional decree, leaving a hope of pardon on repentance; it is absolute, for Ephraim is hopelessly impenitent.