The concept of one God is central to Judaism and Christianity. This concept of one God was actually supposed to be the guiding principle from which all other principles of the Law would be derived. Deuteronomy 6:4-5 states, "Hear of Israel: The LORD our God is one LORD: And thou shalt love the LORD thy God with all thine heart, and with all thy soul, and with all thy might."
Deuteronomy 6:6-9 goes on to reveal how important this concept of one God was to Israel. Not only were the people of Israel to love the Lord with all their hearts, souls, and might, but the words were to be in their hearts. They were to teach the oneness of God to their children at all times: sitting in their house, walking outside, before they went to bed, and when they woke up.
Also notice that the Bible says that they were to bind these words for a sign upon their hands (it was to guide all their actions), have them as frontlets between the eyes (to guide where they looked), write them on the posts of their houses (it was to be remembered and honored where they lived) and upon their gates (remember when you go out and come in). The idea that the Lord was actually conveying to Israel was that the guiding principle of life is that God is one.
Since Christianity is based on the foundation of Judaism and the God of Abraham and Moses, these same principles apply to Christians today. We should love the Lord with all our hearts, souls, and might, but also be guided in what we do, where we look, and where we live by the principle that there is only one God that was manifested in the person of Jesus Christ for our salvation (I Timothy 3:16).
