Charles H. Spurgeon on Psalms 86:16

There is no stronger argument of God's infallible readiness to grant our requests, than the experience of his former concessions. So David reasons, "The Lord that delivered me out of the paw of the lion, and out of the paw of the bear, he will deliver me out of the hand of this Philistine", 1Sa 17:37. This is the argument a priori, the voice of a strong faith, that persuades the conscience God will be gracious to him, because he hath been gracious. The prophet thus often comforted his soul: "Thou hast enlarged me when I was in distress"; therefore, "have mercy upon me, and hear my prayer", Ps 4:1. So, Thou hast delivered my soul from the lowest hell; therefore, O turn unto me, and have mercy upon me. Let the justiciaries deduce arguments from their own present merits, my soul from God's former mercies. Thou, O Lord, madest me good, restoredst me when I was evil; therefore have mercy upon me, miserable sinner, and give me thy salvation. Thus Paul grounded his assurance: because the Lord had stood with him, and delivered him out of the lion's mouth; therefore the Lord shall deliver me still, from every evil work, and preserve me unto his heavenly kingdom. 2 Ti 4:17-18. —Thomas Adams.