Shama-il Tirmidhi Chapter 10, Hadith Number 10 (80).

Aayeshah Radiallahhu Anha says: “Rasulullah Sayyidina Rasulullah sallallahu alaihe wasallam while combing his hair ; wearing his shoes; and while washing his limbs during wudu, as far as possible began with his right.”

This is not confined to the above three only, but covers all other acts as stated previously. The saying, As far as possible, means that for some unforeseen reason he began from the left, then there is no harm.