SB 9.9.29
esa hi brahmano vidvams
tapah-sila-gunanvitah
ariradhayisur brahma
maha-purusa-samjñitam
sarva-bhutatma-bhavena
bhutesv antarhitam gunaih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Here is a learned, highly qualified brahmana, engaged in performing austerity and eagerly desiring to worship the Supreme Lord, the Supersoul who lives within the core of the heart in all living entities.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The wife of the brahmana did not regard her husband as a superficial brahmana who was called a brahmana merely because he was born of a brahmana family. Rather, this brahmana was actually qualified with the brahminical symptoms. Yasya yal laksanam proktam (Bhag. 7.11.35). The symptoms of a brahmana are stated in the sastra:
samo damas tapah saucam
ksantir arjavam eva ca
jñanam vijñanam astikyam
brahma-karma svabhavajam
“Peacefulness, self-control, austerity, purity, tolerance, honesty, wisdom, knowledge, and religiousness — these are the qualities by which the brahmanas work.” (Bg. 18.42) Not only must a brahmana be qualified, but he must also engage in actual brahminical activities. Simply to be qualified is not enough; one must engage in a brahmana’s duties. The duty of a brahmana is to know the param brahma, Krsna (param brahma param dhama pavitram paramam bhavan). Because this brahmana was actually qualified and was also engaged in brahminical activities (brahma-karma), killing him would be a greatly sinful act, and the brahmana’s wife requested that he not be killed.