The covenant of God with His people is encapsulated in one word ‘obedience’. Therefore in Isaiah 1:19, it is written ‘If you are willing and obedient, you will enjoy the good of the land.’ This is further emphasised in the words of Moses which proceeded the blessing or curses presented in Deuteronomy 28, where the underlying key was obedience.
In the Book of Tobit today, we read
For they disobeyed thy commandments, and thou gave us over to plunder, captivity, and death; thou made us a byword of reproach in all the nations among which we have been dispersed' (Tobit 3:4)
Having earlier established the terms of the covenant, when one voluntarily defies the terms involved, they are saying that anything outside the terms of the covenant is allowed to happen.
Look at it this way: whenever a peace treaty is in place, there are terms that are included. A break in even the smallest of clauses is permission for whatever is not contained in the treaty to be executed. For us, just like with Israel, God had promised life, abundance, and freedom; these were encapsulated in their covenant with Him.
However, with their disobedience, the things not included with the covenant namely captivity, plunder and death, could enter their camp. Beloved, ‘Obedience’ does seem like a small word, but it is very weighty. In matters of the kingdom, obedience is the key that keeps us within the boundaries of the promises of God. With every act of rebellion, the boundaries remain in the same place but we voluntarily step out of the provisions within it and expose ourselves to the dangers outside it.
The message is this ‘if you are willing and obedient, you will enjoy the good of the land, and the blessings as listed in Deuteronomy 28 and more, are in effect. On the other hand, if we opt to rebel, then we give permission to experience all that is outside of the covenanted promises. But there is always room to obey and step back across into the boundary of the covenant.