‘The ram's horn to your mouth!
Like an eagle he comes against the house of YHWH,
Because they have transgressed my covenant,
And trespassed against my law.
The opening lines are brief and to the point, being literally:
‘ “The ram's horn to your mouth!” Like an eagle against the house of YHWH'
In other words the prophet is to sound the alarm (compare Hosea 5:8; Amos 3:6) because in vision the eagle has been sighted, and it is coming against ‘the house of YHWH'. This does not refer to the Jerusalem Temple for that Temple is nowhere under consideration by Hosea, nor does it refer to the Temple at Bethel (or even in Samaria) which were never described as houses of YHWH. Rather ‘YHWH's house' is either the land of Israel (Hosea 9:15) or the people of Israel (Hosea 1:4; Hosea 1:6; Hosea 5:1; Hosea 6:10).
The picture of the eagle swiftly descending on its prey (which is ‘the silly dove' - Hosea 7:11) is taken from Deuteronomy 28:49. It is a part of the Deuteronomic curses on those who ‘do not observe His commandments or His statutes' (Deuteronomy 28:15). Compare also the picture in Ezekiel 17. And here it comes on those who ‘have transgressed My covenant and trespasses against My Law'. It was because Israel were neglecting God's requirements as laid down by the covenant of Sinai (see Hosea 4:2) that they would now be snatched away from their land.