The late Shaykh al-Uthaymeen stated during a tele-link on the 28th July 2000:
“…Likewise I invite you to have respect for those people who have the right that they should be respected, from those between you and whom there is and agreement (of protection) [i.e. Non-Muslims]. For the land which you are living is such that there is an agreement between you and them. If this were not the case they would have killed you or expelled you. So preserve this agreement, and do not prove treacherous to it, since treachery is a sign of the hypocrites, and it is not from the way of the Believers.
And know that it is authentically reported from the Prophet that he said, “Whoever kills one who is under and agreement of protection will not smell the fragrance of Paradise.”
Do not be fooled by those sayings of the foolish people; those who say, ‘Those people are Non-Muslims, so their wealth is lawful for us [i.e. to misappropriate or take by way of murder and killing].’ For by Allaah – this is a lie. A lie about Allaah’s Religion, and a lie in Islamic societies.
So we may not say that it is lawful to be treacherous towards people whom we have an agreement with.
O my brothers. O youth. O Muslims. Be truthful in your buying and selling, and renting, and leasing, and in all mutual transactions. Because truthfulness is from the characteristics of the Believers, and Allaah – the Most High – has commanded truthfulness – in the saying of Allaah – the Most High – “O you who believe – fear and keep you duty to Allaah and be with the truthful” Surah Tawbah (9:119)
And the Prophet encouraged truthfulness and said, “Adhere to truthfulness, because truthfulness leads to goodness, and goodness leads to Paradise; and a person will continue to be truthful, and strive to be truthful until he will be written down with Allaah as a truthful person“.
And he warned against falsehood, and said, “Beware of falsehood, because falsehood leads to wickedness, and wickedness leads to the Fire. And a person will continue lying, and striving to lie until he is written down with Allaah as a great liar.”
O my brother Muslims. O youth. Be true in your sayings with your brothers, and with those Non-Muslims whom you live along with – so that you will be inviters to the Religion of Islaam, by your actions and in reality. So how many people there are who first entered into Islaam because of the behavior and manners of the Muslims, and their truthfulness, and their being true in their dealings.”
Source: Shaikh Ibn Uthaimeen on Interacting With Non-Muslims in Western Countries by Salafi Publications
Related Audio: How the Muslims are to Behave & Live with Non-Muslims by Abu Khadeejah