For when God made promise to Abraham, because He could swear by no greater, He sware by Himself… – Hebrews 6:13

Jesus Christ the same yesterday, and today, and for ever. – Hebrews 13:8

Let us joyfully recollect that the Lord our God has not changed, nay, not in one jot or tittle. He is “the same yesterday, today, and for ever.” There is so far a change in the revelation of Him, that it is brighter now in the person of our Lord and Saviour Jesus Christ, than it could have been through seer and vision; but that should be a motive for increased faith. “His arm is not shortened that He cannot save, neither is His ear heavy that He cannot hear.” This God of Abraham is still almighty, and still in the midst of the covenanted ones. If the ages that have passed over His awful brow could wrinkle it and His strength could decay, then might we also decline in our confidence; but it is not so. He fainteth not, neither is weary. Our behaviour towards Him, therefore, should resemble that of Abraham…we must never dishonour the Lord by unbelief. Doubt everything but God. Let God be true and every man a liar. This the everlasting decree which none can change-Christ must reign; He shall see of the travail of His soul and shall be satisfied; the kings of the earth must bow before Him. Do not doubt it, for God hath sworn by His own life that all flesh shall see His glory. Here is the grand argument for strong faith.

The covenant is not disannulled. Let us go to God with any one promise of it, and we can say to Him, “This is Thy promise in Christ Jesus; and Thou hast not spoken in secret in a dark place and withdrawn Thy word and said to the seed of Jacob, ‘Seek ye My face’ in vain.” Such pleading will prevail. He will never run back from His word. Has He said, and will He not do it? Therefore let us cry, “Remember Thy word unto Thy servant upon which Thou hast caused me to hope.” ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1596.cfm