Kāmil al-Ziyārāt > Eating from any Clay is Unlawful Except the Clay of the Grave of Ĥusain (a.s.), For Verily It Is the Cure
Hadith #2

2 حَدَّثَنِي مُحَمَّدُ بْنُ الْحَسَنِ عَنْ مُحَمَّدِ بْنِ الْحَسَنِ الصَّفَّارِ عَنْ عَبَّادِ بْنِ سُلَيْمَانَ عَنْ سَعْدِ بْنِ سَعْدٍ قَالَ سَأَلْتُ أَبَا الْحَسَنِ (ع) عَنِ الطِّينِ- قَالَ فَقَالَ أَكْلُ الطِّينِ حَرَامٌ مِثْلُ الْمَيْتَةِ وَ الدَّمِ وَ لَحْمِ الْخِنْزِيرِ إِلَّا طِينَ قَبْرِ الْحُسَيْنِ فَإِنَّ فِيهِ شِفَاءً مِنْ كُلِّ دَاءٍ وَ أَمْناً مِنْ كُلِّ خَوْفٍ

2. Muĥammad ibn Ĥasan narrated to me from Muĥammad ibn Ĥasan Al-Šaffār, from ‘Abbād ibn Sulaymān, from Sa’d ibn Sa’d, who said: I asked Abal Ĥasan (Imam Riďā (a.s.)) about (eating) clay. Imam (a.s.) replied, “Eating clay is unlawful just like MǏTAH, blood, and the flesh of a swine, except for the clay of the grave of Ĥusain (a.s.), for verily it contains the cure for every disease and the protection against any fear.”