Why can we trust God's promise to David that his royal family would last forever?
God's promise to David is trustworthy because God cannot lie. In 2 Samuel 7:15–16, He vows that His mercy will not depart from David's line and that David's house, kingdom, and throne will be established forever, culminating in the King of kings coming through that royal family.
Les explains that 2 Samuel 7 records God's promise to David that a royal house, or royal family of kings, would come from his line and rule over Israel, and through that line would one day come the King of kings. That King was Christ, born of Mary with Joseph as His legal father, and both Mary and Joseph come down the royal bloodlines of David and Solomon. Even though Israel would commit iniquity and God would chasten them with the rod of men, God says His mercy would not depart from David as it did from Saul. Verse 16 promises that David's house, kingdom, and throne would be established forever. Les emphasizes that God doesn't lie and cannot lie, so this royal family would continue through history and into eternity, and out of it would come the King of kings and Lord of lords, who will come back to Israel, which is why Israel must be in the Middle East at the time of His coming.
And thine house and thy kingdom shall be established for ever before thee: thy throne shall be established for ever.
What is God's promise to Israel in 2 Samuel 7:16 about David's throne?
God's promise to Israel is that David's house and kingdom would be established ever before Him, and his throne would be established forever. It guaranteed a royal line from David through which the King of kings would come, extending beyond history into eternity; God cannot lie.
Who will come out of David's royal family, and to whom will he come?
Out of David's royal family will come the King of kings, the Lord of lords—Christ, born of Mary with Joseph as legal father. He will come to the nation of Israel, just as He came the first time, and will return to the Mount.