in contrast to this, some have weakened al-Bukhārī's narration connected to ʿAbd Allāh ibn Ṣāliḥ, and the answer can be found in Aḥmad's narration through another route. See my commentary on "Mukhtaṣar al-Bukhārī" (2/20).

"Indeed, 'ʿalayka al-salām' is the greeting of the dead. Indeed, 'ʿalayka al-salām' is the greeting of the dead (three times). When a man meets his Muslim brother, let him say: 'al-salāmu ʿalaykum wa-raḥmat Allāh.'" It was narrated by al-Tirmidhī (2/120) through the route of Khālid al-Ḥadhdhāʾ from Abū Tamīmah al-Hujaymī from a man of his people who said: I sought the Prophet (ṣallá Allāhu ʿalayhi wa-sallam) but could not find him, so I sat down, and there was a group among whom he was, but I did not recognize him, and he was reconciling between them. When he finished, some of them stood with him and said: O Messenger of Allāh! When I saw that, I said: 'ʿalayka al-salām, O Messenger of Allāh, ʿalayka al-salām, O Messenger of Allāh, ʿalayka al-salām, O Messenger of Allāh.' He then mentioned the ḥadīth, and the Prophet (ṣallá Allāhu ʿalayhi wa-sallam) replied to me saying: "wa-ʿalayka wa-raḥmat Allāh, wa-ʿalayka wa-raḥmat Allāh, wa-ʿalayka wa-raḥmat Allāh." And he said: "This is a ḥasan ṣaḥīḥ ḥadīth." It was also narrated by al-Ḥākim (4/186) through the route of Abū al-Silīl from Abū Tamīmah from Jābir ibn Sulaym al-Hujaymī who said: I met the Messenger of Allāh (ṣallá Allāhu ʿalayhi wa-sallam) on one of the roads of Medina, and he was wearing a cotton izār with a wide border. I said: 'ʿalayka al-salām, O Muḥammad, or O Messenger of Allāh!' He said: "'ʿalayka al-salām' is the greeting of the dead, 'ʿalayka al-salām' is the greeting of the dead, 'ʿalayka al-salām' is the greeting of the dead. Say: 'salāmun ʿalaykum, salāmun ʿalaykum, salāmun ʿalaykum,' like this." He said: I asked him about the izār, and he raised his back and took hold of most of his leg and said: "Here, and if you refuse, then here above."