Yahweh, via Hosea, pointed out that their ancestors were like grapes plucked in the wilderness. They were like the first fruits of the first season of a fig tree. In the wilderness, they made a covenant with Yahweh. But then, their ancestors came to Baal-peor, as mentioned in Numbers, chapter 25. There, they intermarried with the women of Moab and worshipped the Canaanite fertility god of Baal. Thus, they consecrated themselves to the shameful Baal god. They became detestable, just like this Baal god. All this happened as they entered the land of Canaan.
Surety is guaranteeing of a loan or the collateral for a loan. Obviously, a good kind person will guarantee a loan for his neighbor. However, there are shameful people out there who will take advantage of this generous guarantee. A sinner and an ungrateful person will waste this guarantee. They will abandon their rescuer. Sirach says that guaranteeing loans for others has led many a prosperous person to be ruined and tossed about like waves on the sea. Some have been exiled and wander from country to country. Quite often the sinner and his actions lead to law suits. Sirach then ends with this cautionary note that you should try to help your neighbor as much as possible, but be careful and not fall yourself.