God’s promise never to leave or forsake the Israelites as they enter the promised land (Deuteronomy 31:8) is in fulfillment of His promises to their ancestors (v. 7). God promised Abraham that his descendants would inherit the land of Canaan after four hundred years in slavery in Egypt (Genesis 15:13; 17:8). And He brought Israel out of slavery so they could trust Him as they entered the promised land.
Centuries later, those who are believers in Jesus are also regarded as children of Abraham and share in His inheritance of the whole world (Romans 4:13). Just as God promised to be with Israel as they took hold of their inheritance (Deuteronomy 31:6; Hebrews 13:5), so He’ll be with us (Matthew 28:20).