SB 12.8.15

etat purandaro jñātvā
 saptame ’smin kilāntare
tapo-viśaṅkito brahmann
 ārebhe tad-vighātanam
Synonyms: 
etat — this; purandaraḥ — Lord Indra; jñātvā — learning; saptame — in the seventh; asmin — this; kila — indeed; antare — reign of Manu; tapaḥ — of the austerities; viśaṅkitaḥ — becoming fearful; brahman — O brāhmaṇa Śaunaka; ārebhe — he set into motion; tat — of that austerity; vighātanam — obstruction.
Translation: 
O brāhmaṇa, during the seventh reign of Manu, the current age, Lord Indra came to know of Mārkaṇḍeya’s austerities and became fearful of his growing mystic potency. Thus he tried to impede the sage’s penance.