Charles H. Spurgeon on Psalms 89:30

If his children forsake my law, and walk not in my judgments. It was possible, terribly possible, that David's posterity might wander from the Lord; indeed they did so, but what then? Was the mercy of God to pass away from David's seed? —far from it. So, too, the seed of the Son of David are apt to start aside, but are they therefore cast away? Not a single word gives liberty for such an idea, but the very reverse. Expositors in their fear of Calvinistic doctrine shake off the fear of adding to the word of God, or else they would not have spent their time in talking about "the conditions" of this absolutely unconditional covenant.