CC Ādi 17.24
“The use of the word ‘kevala’ [‘only’] prohibits all other processes, such as the cultivation of knowledge, practice of mystic yoga, or performance of austerities and fruitive activities.
Our Kṛṣṇa consciousness movement stresses the chanting of the Hare Kṛṣṇa mantra only, whereas those who do not know the secret of success for this Age of Kali unnecessarily indulge in the cultivation of knowledge, the practice of mystic yoga or the performance of fruitive activities or useless austerities. They are simply wasting their time and misleading their followers. When we point this out very plainly to an audience, members of opposing groups become angry at us. But according to the injunctions of the śāstras, we cannot make compromises with these so-called jñānīs, yogīs, karmīs and tapasvīs. When they say they are as good as we are, we must say that only we are good and that they are not good. This is not our obstinacy; it is the injunction of the śāstras. We must not deviate from the injunctions of the śāstras. This is confirmed in the next verse of the Caitanya-caritāmṛta.