[The LORD] said, “Surely they are My people, sons who will not be false to Me”; and so He became their Saviour. Isaiah 63:8
You don’t have to read very far into the first books of the Bible to learn that the people of Israel did not live up to God’s expectations. The Lord Himself says as much just a couple sentences later in Isaiah 63. But that is one of the wonderful lessons of the Old Testament – God does not choose His people because they are any better or worse than others. God chooses them because they need a Saviour.