Psalm 89:34: My covenant will I not break, nor alter the thing that is gone out of my lips.
God always keeps His covenant. He does not break any promise that He makes. There will be delays sometimes because of our negligent or less-faith attitude. God promised Abraham that he will be blessed with a son. It did not happen immediately. He had to wait patiently for that promise for more than two decades. In the process of waiting, so many things happened but Abraham did not give up on his faith in the one who promised.
The psalmist, David here says that God said He will not break His covenant nor alter or change the words that He spake from His lips. God is not a man to lie. God shows mercy and kindness to everyone who trusts Him. He shows He is faithful to those who obey His commandments to a thousand generations. God does not have moodswings. He does not say one thing now and another thing some time later. He does not go into depression or recover from lightheadednes or try to recollect what He had spoken a day or two before His promise. He does not change one word of what He has already spoken. Can you find anybody like this in the world? God also says that His word will not return void. It will accomplish the purpose for what it is sent for. If God has spoken that He will promote or bless someone and when those words go out of His mouth, they will accomplish God’s order or command. They never go back to God empty or void.
Learn to take God at His word. It may sometimes look like you have to wait a long, long time for your promise. Do not focus on the waiting time but instead focus on the one who has promised that. He will never fail you.