Where in the Quran does it say that owning a dog is "haram"?

I honestly don't think there are any verses that specifically talk about this. But owning a guard dog is fine since it helps blind people get around. Of course Islam allows keeping dogs, but outside people's premises. And for Muslims, they pray in the house and do you think its fine for, for example if a dog leaps on to you while you're praying, or just comes in front while you're praying? Its a matter of common sense really. Keeping pets isn't even prohibited in Islam. and the Qur'an doesn't either.