Jami` at-Tirmidhi Book 47, Hadith 353
A Jew came to the Prophet of Allah and his Companions and said: “As-Samu Alaikum (Death be upon you).” So the people replied to him. The Prophet of Allah said: “Do you know what this person said?” They said: “Allah and His Messenger know better – he said the Salam – O Allah’s Prophet.” He said: “No, rather he said like this and that. Bring him back for e=me.” So they brought him back and he said: “Did you say As-Samu Alaikum? He said: “Yes.” So with that Allah’s Prophet said: “When one of the People of the Book gives you the Salam, then say: “Alaika Ma Qulta (Whatever you said to you too).” He said: ‘And when they come to you, they greet you with a greeting wherewith Allah greets you not.’
“When (the following) was revealed: ‘O you who believe! When you consult the Messenger in private, spend something in charity before your private consultation.’ The Prophet said to me: ‘What do you think? A dinar?’ I said: ‘They will not be able to.’ He said: ‘Then half a Dinar?’ I said: ‘They will not be able.’ He said: ‘Then how much?’ I said ‘A barely corn.’ He said: ‘You made it too little.’” He said: “So the Ayah was revealed: ‘Are you afraid of spending in charity before your private consultation?’ He said: “It was about my case for which Allah lightened the burden upon this Ummah.”
“The Messenger of Allah ordered burning and cutting down the date palms of Banu An-Nadir, and that (place was called Al-Buwairah. So Allah revealed: What you cut down of the Linah, or you left of them standing on their trunks, it was by the leave of Allah, and in order that He might disgrace the rebellious.”