The Patna Dharmapada 72

72

Uv33:64
yasya dharmaṃ vijānīyād vṛddhasya daharasya vā |
satṛatyanaṃ namasyeta hy agnihotram iva dvijaḥ ||

Uv 33.64
From whomsoever one might understand the dharma, whether from an elder or from a youth, / one should revere him respectfully, as a twice-born does the sacrificial fire.