SB 4.19.15

vadhān nivṛttaṁ taṁ bhūyo
 hantave ’trir acodayat
jahi yajña-hanaṁ tāta
 mahendraṁ vibudhādhamam
Synonyms: 
vadhāt — from killing; nivṛttam — stopped; tam — the son of Pṛthu; bhūyaḥ — again; hantave — for the purpose of killing; atriḥ — the great sage Atri; acodayat — encouraged; jahi — kill; yajña-hanam — one who impeded the performance of a yajña; tāta — my dear son; mahā-indram — the great heavenly King Indra; vibudha-adhamam — the lowest of all demigods.
Translation: 
When Atri Muni saw that the son of King Pṛthu did not kill Indra but returned deceived by him, Atri Muni again instructed him to kill the heavenly King because he thought that Indra had become the lowliest of all demigods due to his impeding the execution of King Pṛthu’s sacrifice.