‘Abdullāh ibn ‘Umar (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) said: "Tayammum is two strikes (of the earth): one strike for the face and one strike for the hands up to the elbows."
عن عبد الله بن عمر - رضي الله عنهما- قال: قال رسول الله -صلى الله عليه وسلم-: «التيمُّمُ ضربتانِ: ضربةٌ للوجه، وضربةٌ لليدين إلى المرفقين».
شرح الحديث :
The noble Hadīth explains the manner of Tayammum, and that it is basically two strikes of the earth; the face is wiped with the first one and the hands up to the elbows are wiped with the second one. This Hadīth is weak. What is correct is that one strike is enough for the face and also the hands up to the wrist, according to the Hadīth of ‘Ammār ibn Yāsir (may Allah be pleased with him): "It would have been sufficient for you to do this with your hands." [Al-Bukhāri and Muslim]