Vaishnava Samhita. Chaturbhujadasa Charitam. Vol III Book VII Chp 12 Shlokas 16 - 17

कृष्णं श्रीनाथमादाय विद्ठले मधुरां गते |

चतुर्थुजः प्राप दुःखं विरहेण सुदुःसहम् ||

अन्यत्र बृन्दाविपिनाद्विपद्यपि न गच्छति |

एतन्महाव्रतं तस्य भक्तस्य व्रजवासिनः ||

Once, Vitthalanatha left for Mathura, taking Shrinatha with him. Chathurbhujadasa got afflicted with grief born of separation from the two. That bhakta had taken a vow not to leave Shri Brindavan even if he were to face any serious difficulty or danger.