Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
abudawud:5199 – Yaḥyá b. Ḥabīb b. ʿArabī > Rawḥ > Ibn Jurayj > Ziyād > Thābit a freed slave of ʿAbd al-Raḥman b. Zayd > Abū Hurayrah

one who is riding should salute one who is walking. He then mentioned the rest of the tradition.  

أبو داود:٥١٩٩ – حَدَّثَنَا يَحْيَى بْنُ حَبِيبِ بْنِ عَرَبِيٍّ أَخْبَرَنَا رَوْحٌ حَدَّثَنَا ابْنُ جُرَيْجٍ قَالَ أَخْبَرَنَا زِيَادٌ أَنَّ ثَابِتًا مَوْلَى عَبْدِ الرَّحْمَنِ بْنِ زَيْدٍ أَخْبَرَهُ أَنَّهُ سَمِعَ أَبَا هُرَيْرَةَ يَقُولُ

قَالَ رَسُولُ اللَّهِ ﷺ يُسَلِّمُ الرَّاكِبُ عَلَى الْمَاشِي ثُمَّ ذَكَرَ الْحَدِيثَ