Srimad-Bhagavatam (12.3.51–52):
kaler dosa-nidhe rajann asti hy eko mahan gunah
kirtanad eva krsnasya mukta-sangah param vrajet
krte yad dhyayato visnum tretayam yajato makhaih
dvapare paricaryayam kalau tad dhari-kirtanat
"The most important factor in this Age of Kali, which is an ocean of faults, is that one can be free from all contamination and become eligible to enter the kingdom of God simply by chanting the Hare Krsna mantra. The self-realization that was achieved in the Satya millennium by meditation, in the Treta millennium by the performance of different sacrifices, and in the Dvapara millennium by worship of Lord Krsna can be achieved in the Age of Kali simply by chanting the holy names, Hare Krsna."