From the Prashna Upanishad

Six questions for Pippalada

Six students who had studied the Vedas came to the sage Pippalada, each with a bundle of firewood and a question. He made them wait a year before they could ask. These are the six questions and his answers, told simply.

Six studentsKabandhi, Bhargava, Kausalya, Gargya, Satyakama, Sukesha
Pippaladaa forest sage who makes his students wait
A U M ॐ Six students with firewood