Our Unchanging God

Our God is unchanging.
For I am the LORD, I change not; therefore ye sons of Jacob are not consumed. (Malachi 3:6 KJV)
Jesus Christ is the same yesterday and today and forever. (Hebrews 13:8 ESV)

He keeps His promises.
God is not man, that he should lie, or a son of man, that he should change his mind. Has he said, and will he not do it? Or has he spoken, and will he not fulfill it? (Numbers 23:19 ESV)
And also the Strength of Israel will not lie nor repent: for he is not a man, that he should repent. (1 Samuel 15:29 KJV)

He even confirmed it with an oath.
For example, there was God's promise to Abraham. Since there was no one greater to swear by, God took an oath in his own name, saying: "I will certainly bless you, and I will multiply your descendants beyond number." Then Abraham waited patiently, and he received what God had promised. Now when people take an oath, they call on someone greater than themselves to hold them to it. And without any question that oath is binding. God also bound himself with an oath, so that those who received the promise could be perfectly sure that he would never change his mind. So God has given both his promise and his oath. These two things are unchangeable because it is impossible for God to lie. Therefore, we who have fled to him for refuge can have great confidence as we hold to the hope that lies before us. (Hebrews 6:13-18 NLT)

Our faith and hope lies in His faithfulness.
It is of the Lord's mercies that we are not consumed, because his compassions fail not. They are new every morning: great is thy faithfulness. (Lamentations 3:22-23 KJV)
If we are faithless, He remains faithful, for He cannot deny Himself. (2 Timothy 2:13 NASB)
What if some were unfaithful? Does their faithlessness nullify the faithfulness of God? By no means! Let God be true though every one were a liar, as it is written, "That you may be justified in your words, and prevail when you are judged." (Romans 3:3-4 ESV)