The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, narrated to me from Abu al-Qasim Ja'far ibn Muhammad, from his father, from Muhammad ibn al-Hasan al-Saffar, from Ahmad ibn Muhammad, from al-Husayn ibn Sa'id, from Safwan, from Amr ibn Abi al-Miqdam: Abu Abdullah عليه السلام was asked to described Tayammum (dry ablution). Imam عليه السلام struck his hands on the ground, then lifted them and shook them off. Imam عليه السلام then wiped his forehead and his palms with them once.