Vaishnava Samhita. Chaturbhujadasa Charitam. Vol III Book VII Chp 12 Shlokas 7 - 8

न मन्त्रेण न संस्कारात् कुलेनापि न वैष्णवः |

विष्णुभक्तिर्यदि दृढा स हि श्रीवैष्णवोत्तमः ||

महतां वैष्णवानां तु कुले जातो यदृच्छया |

न करोति हरौ भक्तिं यदि नीचाधमः स्मृतः ||

One is not considered a vaishnava because of high birth or adherence to rituals or knowledge of mantras. One who has unwavering Vishnu bhakti alone becomes a vaishnavottama. One who is born in a reputed vaishnava clan and yet fails to develop Hari bhakti is really considered a low-born.