Gen. 28:20-21 Then Jacob made this vow: "If God will be with me and protect me on this journey and give me food and clothing, and if he will bring me back safely to my father, then I will make the Lord my God."
Jacob was on a mission. He had left home and was on a journey to find a wife from amongst his cousins in Paddan-aram. Isaac had sent him on his way after Rebekah had persuaded Isaac to not let Jacob marry a local girl. She was concerned for Jacob's safety since Esau had vowed that he would take revenge on Jacob and kill him for robbing him of his birthright and blessings.
While on his way he stopped to spend the night at Bethel where an angel visited with him in a dream. Jacob must have been afraid and had a lot of questions go through his mind. He was on the run for his life, he was visited by an angel who told him that God was going to fulfill His promise to Abraham and Isaac through him, and he did not know what lied before him. What kind of a girl would he find? Would he love her and would she love him? Would he ever return home? Would Esau chase after him? What if his mission was a failure? Would God really keep His promise to him?
Jacob then made a vow that if things worked out and God did make his journey successful, that he would make Him his God and Lord. Up until this time Jacob had not fully committed himself to the Lord. He knew that God was, but He was not yet his. He still believed that God was his because Isaac and Rebekah had faith in Him.
It's not good enough to believe that God is, we must personally embrace Him. We must make a life commitment to Him. We must develop a personal relationship with Him by giving Him all of our heart, mind and soul. We must give Jesus full access to our heart. We must confess all of our sins to Him and ask for His forgiveness. We must then determine in our heart that we will no longer travel down the pathway of sin. We then must strive to live humbly and obediently to Him in holiness of heart. It is then, and only then, that we can honestly declare that God is ours and we are His.