Imam Aḥmad said, “Whoever claims that tayammum must be extended to the elbows has added something of his own.”

Disagreement among the scholars
The jurists have differed over how tayammum is to be performed:
• Imam Aḥmad holds that the prescribed form is a single strike. One wipes the face with the pads of the fingers and wipes the palms with the inner surfaces of the opposite hand. It is not sunnah to wipe the forearms up to the elbows; the wiping stops at the wrists. This is the sound and famous view in his school.
Al-Tirmidhī said: “More than one scholar among the Companions and the Followers held this opinion—among them ʿAlī, ʿAmmār, Ibn ʿAbbās, ʿAṭāʾ, al-Shaʿbī and Isḥāq. It was also chosen by Ibn al-Mundhir, the Ẓāhirīs, the hadith jurists, Shaykh al-Islām Ibn Taymiyyah, Ibn al-Qayyim and al-Shawkānī, and it is the practice of the Salafi scholars of Najd.”
Their evidence is the hadith of ʿAmmār related by al-Bukhārī (347) and Muslim (368): “The Prophet ﷺ struck the ground with his hands once, then wiped the left over the right, the backs of his hands, and his face.”

• The other three Imams maintain that tayammum requires two strikes: with one the face is wiped, with the other the hands up to the elbows. They cite the hadith under discussion, “Tayammum is two strikes—one for the face and one for the hands up to the elbows,” and a similar report narrated by al-Dāraquṭnī from Jābir.
Al-Khallāl remarked, “The reports supporting that are extremely weak; the compilers of the Sunan record only the narration of Ibn ʿUmar, and Imam Aḥmad said it is not authentic from the Prophet ﷺ.”
Even supposing such narrations were fit to be cited, they cannot override what is affirmed in the two Ṣaḥīḥs.