The Bible tells us that God is a jealous God: “For thou shalt worship no other god: for the Lord, whose name is Jealous, is a jealous God: (Exodus 34:14). 
God never has been and never will be pleased with anyone or anything taking his place in the heart of man. So let’s look at what place God has in our heart.
When God gave the Ten Commandments to man, he made it plain that nothing was to come before him. “And God spoke all these words, saying, I am the Lord thy God, which have brought thee out of the land of Egypt, out of the house of bondage. Thou shalt have no other gods before me. Thou shalt not make unto thee any graven image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth: Thou shalt not bow down thyself to them, nor serve them: for I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me” (Ex. 20:1-5).
As we study the Old Testament, we see that his people did not keep this commandment of God. Time and time again, they were warned by the messengers of God to put away idols and turn back to God, but they refused.
This led to their eventual downfall, as God allowed foreign nations to overtake them.
There are many great lessons in all of this. That is why Paul could say, “For whatsoever things were written aforetime were written for our learning, that we through patience and comfort of the scriptures might have hope” (Romans 15:4).
God still demands that he be put first in the hearts of men today in everything. His desire is for all men to come to him through His Son. 
“Jesus saith unto him, I am the way, the truth and the life: No man cometh unto the Father, but by me” (John 14:6). 
His jealousy will not tolerate those who would try to come to him by a different way.
Men down through history have tried to come up with their way of getting to God. Even when Christ was upon the earth, men were teaching things contrary to God’s commandments.
“But in vain they do worship me, teaching for doctrines the commandments of men” (Matt. 15:9). Man was not and is not capable of coming up with a “saving plan” on his own. 
Jeremiah the prophet recorded these words by inspiration, “O Lord, I know that the way of man is not in himself: It is not in man that walketh to direct his steps” (Jer. 10:23).
God’s plan for man’s salvation has been in the mind of God from the beginning, and he has marvelously and wondrously worked out his plan for man.
This is why Jesus was able to say, “Not everyone that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? And in thy name have cast out devils? And in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity” (Matt. 7:21-23).
God’s plan is seen in how those in the first century obeyed the gospel. They believed in Christ as God’s Son; they willingly repented of their sins, confessed the name of Christ before men and were baptized for the remission of their sins.
Where is God in your heart?