Beware of upstart spiritual groups

One who is serious about receiving transcendental Vedic knowledge must accept a guru, or spiritual master, in one of these four disciplic successions. It is said that unless one accepts a mantra from one of these sampradayas, the so-called mantra will not act in Kali-yuga. Many sampradayas have sprung up without authority, and they are misleading the people by giving unauthorized mantras. The rascals of these so-called sampradayas do not observe the Vedic rules and regulations. Although they are addicted to all kinds of sinful activities, they still offer the people mantras and thus mislead them. Intelligent persons, however, know that such mantras will never be successful, and as such they never patronize such upstart spiritual groups. People should be very careful of these nonsensical sampradayas. To get some facility for sense gratification, unfortunate people in this age receive mantras from these so-called sampradayas.

Srimad Bhagavatam 4.17.5 purport