It is mentioned in Padma Purana that:
sampraya-vihina mantraste nishphala matah
sadhanoghaih na siddayanti koti-kalpashtairapi
"If mantras are not received in a traditional lienage or sampradaya, they are fruitless. By practicing such mantras, one cannot achieve perfection even in a very long period of time."
atah kalau bhavishyanti chatvarah sampradayinah
sri-brahma-rudra-sanaka vaishnava kshiti-pavanah
"In order to get perfection from the mantra, one must receive initiation from a guru of a authorized lineage or sampradaya. Therefore in Kaliyuga, as far as Vaishnavism is concerned, there are four eternal sampradayas, namely Sri, Brahma, Rudra and Sanaka*."
* Sanaka Kumara.