SB 6.13.11
tayendrah smasahat tapam
nirvrtir namum avisat
hrimantam vacyatam praptam
sukhayanty api no gunah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Following the advice of the demigods, Indra killed Vrtrasura, and he suffered because of this sinful killing. Although the other demigods were happy, he could not derive happiness from the killing of Vrtrasura. Indra’s other good qualities, such as tolerance and opulence, could not help him in his grief.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
One cannot be happy by committing sinful acts, even if one is endowed with material opulence. Indra found this to be true. People began to blaspheme him, saying, “This person has killed a brahmana for the sake of enjoying heavenly material happiness.” Therefore in spite of being King of heaven and enjoying material opulence, Indra was always unhappy because of the accusations of the populace.