1 Samuel 15: 29 NLT
And he who is the Glory of Israel will not lie, nor will he change his mind, for he is not human that he should change his mind!
This verse is an important verse for each of us to know and understand. Without it, much of the Bible loses its efficacy. However, with it, the Old Testament is as vibrant and life giving as the New Testament.
This verse tells that God does not lie. Truth be told, He cannot lie because whatever He says simply becomes. Whatever He speaks comes into being. Besides that, there is nothing which intimidates Him into lying. Why should He lie? He is God after all. This means that we can hold Him to whatever He says. Moreover, since He does not change His mind, whatever He has ever said is as viable as the moment it was spoken.
There is great power in this verse because it means you have an entire book of promises that are available to you. You may enter His throne room and put in your request according to the promise already given.
One other little thought – I think it interesting to see the Father called the Glory of Israel. I would argue that we are a part of the new Israel according to the redemption we received in Christ. So, He is our glory and that is a wonderful name and idea to wrap your head around.