Sahih Muslim Book 42, Hadith Number 7145.

Chapter : The older one is to be preferred.

‘Abdullah b. Umar reported that Allah’s Messenger (may peace be upon him) said: It was shown in a vision that I was rinsing my mouth with miswak and two persons began to contend with one another for getting that miswak. One was older than the other. I gave the miswak to the younger one amongst them, but it was said to me: (Let it be given) to the older one. So I gave it to the older one.