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.
ibnmajah:1561al-ʿAbbās b. Jaʿfar > Muḥammad b. Ayyūb Abū Hurayrah al-Wāsiṭī > ʿAbd al-ʿAzīz b. Muḥammad > Kathīr b. Zayd > Zaynab b. Nubayṭ > Anas b. Mālik

It was narrated from Anas bin Malik that the Messenger of Allah ﷺ marked the grave of ‘Uthman bin Maz’un with a rock.  

ابن ماجة:١٥٦١حَدَّثَنَا الْعَبَّاسُ بْنُ جَعْفَرٍ حَدَّثَنَا مُحَمَّدُ بْنُ أَيُّوبَ أَبُو هُرَيْرَةَ الْوَاسِطِيُّ حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ مُحَمَّدٍ عَنْ كَثِيرِ بْنِ زَيْدٍ

عَنْ زَيْنَبَ بِنْتِ نُبَيْطٍ عَنْ أَنَسِ بْنِ مَالِكٍ أَنَّ رَسُولَ اللَّهِ ﷺ أَعْلَمَ قَبْرَ عُثْمَانَ بْنِ مَظْعُونٍ بِصَخْرَةٍ