Purity: Obligation to Wash the Right and Left Arms in Sequence During Wuḍūʾ

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 244

After washing the face, one must wash his right arm from the elbow to the tips of the fingers, and he must then proceed to wash his left arm in the same way.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)