Hadith: Do not say "upon you be peace"; "Upon you be peace" is how you greet the dead. Say instead "peace be upon you"

عن أبي جرَيٍّ جابر بن سُلَيْمٍ رضي الله عنه قال: رأيت رجلاً يصْدُرُ الناس عن رأيه، لا يقول شيئاً إلا صدروا عنه، قلت: من هذا؟ قالوا: رسول الله صلى الله عليه وسلم . قلت: عليك السلام يا رسول الله - مرتين - قال: «لا تقل: عليك السلام، عليك السلام تحية الموتى، قل: السلام عليك» قال: قلت: أنت رسول الله؟ قال: «أنا رسول الله الذي إذا أصابك ضُرٌّ فدعوته كشفه عنك، وإذا أصابك عام سَنَةٍ فدعوته أنْبَتَهَا لك، وإذا كنت بأرض قَفْرٍ أو فَلَاةٍ فَضَلَّتْ راحلتك، فدعوته ردها عليك» قال: قلت: اعْهَدْ إِليَّ. قال: «لا تَسُبَنَّ أحداً» قال: فما سَبَبْتُ بعده حُرًّا، ولا عبداً، ولا بعيراً، ولا شاة، «ولا تحْقِرَنَّ من المعروف شيئاً، وأن تكلم أخاك وأنت مُنْبَسِط إليه وجهك، إنَّ ذلك من المعروفِ، وارفعْ إزارك إلى نصف الساق، فإِنْ أبيت فإلى الكعبين، وإياك وإسبال الإزار، فإنها من المَخِيلَةِ. وإِنَّ اللهَ لا يحب المَخِيلَةَ؛ وإِنِ امرُؤٌ شتمك وعَيَّرَكَ بما يعلم فيك فلا تُعَيِّرْهُ بما تعلم فيه، فإِنَّما وبال ذلك عليه».
[صحيح] - [رواه الترمذي وأبو داود وأحمد]

Abu Jarai Jābir ibn Sulaym (may Allah be pleased with him) reported: I saw a man whose opinion was followed by the people, and whenever he said something they acted in accordance to what he said. I asked: "Who is that?" They said: "The Messenger of Allah (may Allah's peace and blessings be upon him)." I said to him twice: "Upon you be peace, O Messenger of Allah." He said: "Do not say 'upon you be peace'; 'Upon you be peace' is how you greet the dead. Say instead 'peace be upon you.'"
Sahih/Authentic. - [At-Tirmidhi]

Explanation

Jābir ibn Sulaym (may Allah be pleased with him) reported that he saw a man whose opinion was followed by everyone and no one would contradict what he said. He asked the people who he was and they replied that he is the Messenger of Allah (may Allah's peace and blessings be upon him). So he greeted him twice, saying: "Upon you be peace, O Messenger of Allah." The Messenger of Allah (may Allah's peace and blessings be upon him) answered: "Do not say 'upon you be peace'; 'Upon you be peace' is how you greet the dead. Say instead 'peace be upon you.'" Jābir then asked: "Are you the Messenger of Allah?" He said: "Yes, I am the Messenger of Allah." i.e. I am he who was sent by Allah; Allah is He who will lift your affliction when you call upon him if you're afflicted with poverty or a calamity, who will cause the plants to grow to give you food when you call upon him at times of famine, and who will restore to you your riding animal when you call upon him if it has abandoned you in a desolate land in which there are no people and no water. Jābir then asked him to give him advice, and he told him not to curse anyone. Jābir said that he never cursed anyone since then, neither a freeman, nor a slave, nor a camel, nor a sheep. The Messenger of Allah then told him: Do not look down upon any good deed or refrain from doing it because you think it is insignificant, even addressing your fellow Muslim with a cheerful face for that is an act of goodness. Keep the length of your Izār (waist sheet) midway down the shin (and not farther). If not, then down to the ankles (but not lower than that). There is no harm in letting the garment reach between the ankles and halfway up the shin, but beware of letting your garment trail lower than that for it represents arrogance and pride, and Allah, the Almighty loathes this. If someone insults you mentioning your sins and bad deeds that you commit, do not insult him back with his own sins and bad deeds. He will receive punishment for what he said on the Day of Judgment and he may even see some of his punishment in the life of this world.