Narrated Anas bin Malik:
Allah's Apostle said, "I have been ordered to fight the people till they say: 'None has the right to be worshipped but Allah.' And if they say so, pray like our prayers, face our Qibla and slaughter as we slaughter, then their blood and property will be sacred to us and we will not interfere with them except legally and their reckoning will be with Allah."
Narrated Maimun ibn Siyah that he asked Anas bin Malik, "O Abu Hamza! What makes the life and property of a person sacred?"
He replied, "Whoever says, 'None has the right to be worshipped but Allah', faces our Qibla during the prayers, prays like us and eats our slaughtered animal, then he is a Muslim, and has got the same rights and obligations as other Muslims have."