Muhammad bin Ziyad al-Alhani (may Allah have mercy on him) narrates about Sayyiduna Abu Umamah al-Bahili (may Allah be pleased with him) that he used to greet everyone he met with salam. The narrator said: I never saw anyone get ahead of him in giving the greeting, except once a Jew who hid from him behind a pillar, then came out and greeted him. Abu Umamah (may Allah be pleased with him) said to him: Woe to you, O Jew! What made you do what you did? He said: I saw that you are a man who gives the greeting a great deal, so I knew that it is a virtue, and I wanted to adopt it. At this Sayyiduna Abu Umamah (may Allah be pleased with him) said: Woe to you! I heard the Messenger of Allah (peace and blessings be upon him) say: "Allah has made the salam a greeting (tahiyyah) for our Ummah and a guarantee of safety for the protected people (ahl al-dhimmah) under us."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7487