CC Ādi 17.161

ataeva jarad-gava māre muni-gaṇa
veda-mantre siddha kare tāhāra jīvana
ataeva — therefore; jarad-gava — old cows; māre — killed; muni-gaṇa — sages; veda-mantre — by the power of Vedic hymns; siddha — rejuvenated; kare — makes; tāhāra — his; jīvana — life.
“Therefore the great sages sometimes killed old cows, and by chanting Vedic hymns they brought them back to life for perfection.