A report attributed to Ammar ibn Yasir is cited with the wording:
تَكْفِيكَ ضَرْبَةٌ لِلْوَجْهِ، وَضَرْبَةٌ لِلذِّرَاعَيْنِ
Meaning: One strike for the face and one strike for the forearms are sufficient.
Jurists favoring two strikes use such reports, while other transmissions mention one strike. The strength and legal implications of these transmissions are discussed differently.