Israel was holiness, etc. Israel was a consecrated people (comp. Exodus 19:5, Exodus 19:6; Deuteronomy 7:6; Deuteronomy 14:2; Deuteronomy 26:19). Isaiah, fond as he is of the phrase "Israel's Holy One," does not expressly enforce the correlative truth, as Jeremiah does here.
The first-fruits of his increase; rather, his firstfruits of increase. Israel is compared to the firstfruits (reshith) of the land, which were devoted to the house of the Lord (Exodus 23:19; Numbers 18:12, Numbers 18:13).
So in Amos 6:1, the title given him is "the chief [margin, 'firstfruits'] of the nations" (in Jeremiah 31:7, a synonymous and cognate word, rosh, takes the place of reshith for "chief"). All that devour him shall offend; rather, all that ate him incurred guilt, or became guilty of a trespass.
Foreigners were forbidden to eat of consecrated things; by breaking this law they became guilty of a "trespass," having invaded the rights of Jehovah (Le 22:10, 15, 16). The word for "trespass" is the same as that rendered "guilt."