Everyone is required to be obedient to God. God’s children must be obedient. Those not His children must be obedient. Disobedience brings judgment and destruction.
On the other hand, being the people of God carries with it blessings no one else has. God is a great God. He is supreme, the “God of gods and Lord of lords, mighty and awesome.” He set his affection on Israel not because they were a great nation (Deuteronomy 7), nor because they were especially righteous (chapter 9), but simply and solely because He chose to love them.
God has promised special blessings to His people – and only to them and only because they are His people. His requirement of them can be summed up in these words from chapter 10: “fear the Lord, walk in His ways, love Him with all your heart and soul, and obey Him.” This will not bring the blessing of God. The blessing comes solely as a gift and by His grace. These requirements simply keep the blessing from being withdrawn.
Christianity did not change this relationship. Grace is still the reason we are special to God; still the reason for the blessings we have. We love God not to earn His favor, but because He deserves to be loved. We obey Him not to get blessings, but to keep the ones He has already guaranteed.