Why does God require faith?

Put it like this, wouldn't you want your child to have faith in you that you will provide his/her every need? You can't have faith in something you don't believe in. Faith isn't for his well being, it is for our well being. To have faith as big as a mustard seed can get you through all sorts of situations because you believe in a higher power than that of your own understanding. A person that is anti Christ or whatever has to come to know the Lord and Savior themselves. If they are ignorant then they can't be punished or condemned for what they don't know. That is why Jesus said the healthy aren't the ones that need a doctor and the saved are the ones that need Him. http://www.simpleknowlegde.blogspot.com

I would say the answer to this is that the only way that you can believe in God, like love, can only be real if you have faith in it.

God is a spirit,so believe its existence through faith will help us,

Well, Romans 14:23 states that whatever is not of faith is sin. But there's more to it than just that. Faith is also compassion. Jesus was compassionate when he healed or told those with faith in Him that He forgave their sins and healed them. Faith is love, God is love. That which is not of faith is sin, because sin is "missing the mark". You are off course. But even in secular life, we allow free will but within limits. You have the free will to commit murder but the state will probably punish you for it. If you look at basic laws that are universal, they generally punish for acts that are harmful to others: murder, stealing, etc. Therefore, God's eternal laws about love, compassion and faith are actually very consistent with what humans do in their own world.