The Core Statement of the Obligations

Taharah and Wudu Obligations: Limits, Evidence and Juristic Differences

فَرْضُ الطَّهَارَةِ غَسْلُ الْأَعْضَاءِ الثَّلَاثَةِ، وَمَسْحُ الرَّأْسِ

Meaning: The obligation in purification is washing the three limbs and wiping the head.
The three washed areas are the face, both arms, and both feet. Wiping the head is the fourth obligation. The context here is the obligations of wudu.