If Jesus rejected something can it be His word? There is only one God so my God is your God and the God of all whether they believe in one God or not. Christians understand God through the teachings of Jesus. The major reason for Jesus being put to death was his challenge of many religious laws of those days. The world today is much better for it.
Why do many Christians quote from the Old Testament? If it goes against the teachings of Jesus then that has me perplexed too.