In Deuteronomy 6:4-5, we read, "The Lord is our God, the Lord is one!" And Thou shall love the Lord thy God with all your heart, and with all your soul and with all you might.
We don't worship three Gods. God is one in three Persons. Then in Deuteronomy 6:5, the first commandment is described in another way. This is what Jesus quoted in Matthew 22:37: "Love the Lord your God with all your heart and with all your soul and with all your might. "That is the first commandment.
That means that we don't have any place in our hearts for family, property, job, or money - because ALL of our heart is given to God. This is Instruction No.1 in the "Manufacturer's Instruction" Manual. Don't operate the human machine before you have obeyed this commandment.
What will happen when you love the Lord with all your heart?
You will love your wife even better!
You will love your neighbour better.
You will even love your enemies, because you don't have any hatred in your heart anymore.
Jealousy, hatred, bitterness and all other sins against others are caused by not loving God with all your heart. The part of your heart that should be loving God is filled with jealousy. We overcome sin not by battling sin primarily, but by loving God with all our heart. When we love God with all our heart, the love of money and property and evil lusts will all go away.
Consider a girl who is in love with Mr. A, who is not such a good person. Her parents try their best to stop her from loving him but they can't succeed. Then one day this girl meets Mr. B who is far more handsome, richer and a more pleasant person. Suddenly all her love for Mr. A disappears. How did that happen? That can be called "the expulsive power of a new affection". A new love drove out the first love.
Apply this to the Christian life. Here you are lusting after so many evil things that God forbids. You try and try to give up these bad habits but cannot, because you love those lusts. Then one day, you see the glory of Jesus and begin to love Him with all your heart. What happens? This new love has driven out the old affections. Then we have no more interest in the things of this world. It's "the expulsive power of a new affection". This is the secret of victory over sin. Love God with all your heart and with all your soul -
which means with all your intellectual power.
