Charles H. Spurgeon on Psalms 119:86

All thy commandments are faithful. David setteth down here three points. The one is that God is true; and after that he addeth a protestation of his good conduct and guidance, and of the malice of his adversaries: thirdly, he calleth upon God in his afflictions. Now as concerning the first, he showeth us that although Satan to shake us, and in the end utterly to carry us away, subtilly and cunningly goeth about to deceive us, we must, to the contrary, learn how to know his ambushes, and to keep us from out of them. So often then as we are grieved with adversity and affliction, where must we begin? See Satan how he pitches his nets and layeth his ambushes to induce and persuade us to come into them, what saith he? Dost thou not see thyself forsaken of thy God? Where are the promises whereunto thou didst trust? Now here thou seest thyself to be a wretched, forlorn creature. So then thou right well seest that God hath deceived thee, and that the promises whereunto thou trustedst appertain nothing at all unto thee. See here the subtlety of Satan. What is now to be done? We are to conclude with David and say, yet God is true and faithful. Let us, I say, keep in mind the truth of God as a shield to beat back whatsoever Satan is able to lay unto our charge. When he shall go about to cause us to deny our faith, when he shall lie about us to make us believe that God thinketh no more of us, or else that it is in vain for us to trust unto his promises; let us know the clean contrary and believe that it is very plain and sound truth which God saith unto us. Although Satan casteth at us never so many darts, although he have never so exceeding many devices against us, although now and then by violence, sometimes with subtlety and cunning, it seemeth in very deed to us that he should overcome us; nevertheless he shall never bring it to pass, for the truth of God shall be made sure and certain in our hearts. John Calvin.