It is narrated from Sayyiduna Ali (may Allah be pleased with him): There are two strikes: one strike for the face and one strike for the forearms. Both of these (reports) from Sayyiduna Ali (may Allah be pleased with him) are munqati' (broken). (b) Khalid narrates from Abu Ishaq that Sayyiduna Ali (may Allah be pleased with him) said concerning tayammum: One strike for the face and one strike for the palms.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1016