SB 4.25.7

nārada uvāca
bhoḥ bhoḥ prajāpate rājan
 paśūn paśya tvayādhvare
saṁjñāpitāñ jīva-saṅghān
 nirghṛṇena sahasraśaḥ
Synonyms: 
nāradaḥ uvāca — the great sage Nārada replied; bhoḥ bhoḥ — hello; prajā-pate — O ruler of the citizens; rājan — O King; paśūn — animals; paśya — please see; tvayā — by you; adhvare — in the sacrifice; saṁjñāpitān — killed; jīva-saṅghān — groups of animals; nirghṛṇena — without pity; sahasraśaḥ — in thousands.
Translation: 
The great saint Nārada said: O ruler of the citizens, my dear King, please see in the sky those animals which you have sacrificed without compassion and without mercy in the sacrificial arena.
Purport: 

Because animal sacrifice is recommended in the Vedas, there are animal sacrifices in almost all religious rituals. However, one should not be satisfied simply by killing animals according to the directions of the scriptures. One should transcend the ritualistic ceremonies and try to understand the actual truth, the purpose of life. Nārada Muni wanted to instruct the King about the real purpose of life and invoke a spirit of renunciation in his heart. Knowledge and the spirit of renunciation (jñāna-vairāgya) are the ultimate goal of life. Without knowledge, one cannot become detached from material enjoyment, and without being detached from material enjoyment, one cannot make spiritual advancement. Karmīs are generally engaged in sense gratification, and for this end they are prepared to commit so many sinful activities. Animal sacrifice is but one such sinful activity. Consequently, by his mystic power Nārada Muni showed King Prācīnabarhiṣat the dead animals which he had sacrificed.