Mudgalapurana 3.17.46

3.17.46

tretāyāṃ ca dayā naṣṭā naṣṭaṃ ca dvāpare tapaḥ |
ācāraśca kalau prāpte naṣṭarūpo bhaviṣyati ||

And in the Tretā [age] compassion was destroyed, and in the Dvāpara [age] austerity was destroyed; / and when the Kali age has arrived, good conduct will assume a destroyed form.