Chandogya Upanishad 2.14

Rising, the sun is the hinkâra, risen, he is the prastâva, at noon he is the udgîtha, in the afternoon he is the pratihâra, setting, he is the nidhana. That is the Brihat Sâman as interwoven in the sun.

He who thus knows the Brihat as interwoven in the sun, becomes refulgent and strong, he reaches the full life, he lives long, becomes great with children and cattle, great by fame. His rule is, 'Never complain of the heat of the sun.'