Why One God

If we check ourself deeply than we will understand why God saying, that don't make any partner or god with Him Otherwise He will never forgive those who did this

If anyone wife very beautiful, she maintain everything for her husband, she keep good eyes on children of her husband, she always give full service to her husband, If any thing broken (which her husband most like) by her in house, husband will forgive her, or she make any minor mistake , husband will forgive her, But if she look other man except her husband with Love Eyes
I think no Husband will forgive this thing, if he really know what mean of wife

This is the same thing, which God saying to us, O human you can use what the things in this world made by Me (God), or everything which you like to use, but don't make partner or other gods with Me (God)

We all human being must have to consider this point of One God