Bhakti-rasāmṛta-sindhu .2.223
Blended reading (Sanskrit + English inline)
The execution of devotional service during Ūrja-vrata in the month of Kārttika is especially recommended to be performed at Mathurā. This system is still followed by many devotees. They go to Mathurā or Vṛndāvana and stay there during the month of Kārttika specifically to perform devotional services during this period. In the Padma Purāṇa it is said, “The Lord may offer liberation or material happiness to a devotee, but after some devotional service has been executed, particularly in Mathurā during the month of Kārttika, the devotees want only to attain pure devotional service unto the Lord.” The purport is that the Lord does not award devotional service to ordinary persons who are not serious about it. But even such unserious persons who execute devotional service according to the regulative principles during the month of Kārttika, and within the jurisdiction of Mathurā in India, are very easily awarded the Lord’s personal service.
My note
Source: vedabase.io