It is With The Heart A Person Believe

God loves us, not because we love Him.

"In this is love,

not that we loved God,

but that He loved us

and sent His Son 

to be the propitiation for our sins."
1 John 4:10 (NASB)

The Bible says God loved us while we were yet sinners, and He demonstrated His love towards us by sending His only Son Jesus Christ to die for our sins.

"But God demonstrates His own love toward us,

in that while we were yet sinners,

Christ died for us."

Romans 5:8 (NASB)

However, salvation is a gift from God, and this gift is received through faith in Him and not of ourselves.

For by grace

you have been saved through faith;

and that not of yourselves,

it is a gift of God."

Ephesians 2:8 (NIV)

And if we believe in God, we must also believe in His Word because the Word is God. Just believing there is a God is not enough. We must believe His Word, as well. 

"In the beginning was the Word,

and the Word was with God,

and the Word was God."
John 1:1 (NASB)

We can't believe in God and His Word halfheartedly either.  We must love and believe in God and all His Word with our whole hearts.

"That if you confess with your mouth

Jesus as Lord,

and believe in your heart that God raised Him from the dead,

you will be saved;

for with the heart a person believes,

resulting in righteousness,

and with the mouth he confesses,

resulting in salvation."

Romans 10:9-10 (NASB)

It is with the heart a person believes, resulting in righteousness, and with the mouth he/she confesses, resulting in salvation. The gift of salvation starts with the heart of God, but it is received by the hearts of man. God gave up His life for us so that we may be saved, but we must now give up our hearts to Him to receive this salvation from God.