Qualification to hear about mādhura rati

In Bhakti-rasāmṛta-sindhu, the five chief types of sacred feelings with all their component ingredients are described in a comprehensive manner. Sacred erotic love (madhurā rati) has there been characterized as standing above all other kinds of sacred attitude towards the Supreme; nevertheless, it was only summarized there briefly as Rūpa reserved his extensive treatment of the subject for the exhaustive Ujjvala-nīlamaṇi.

Rūpa himself explains why:

nivṛttānupayogitvād durūhatvād ayaṁ rasaḥ |
rahasyatvāc ca saṁkñipya vitatāṇgo vilikhyate || Bhakti-rasāmṛta-sindhu, 3.5.2.

Three types of person are unqualified to hear about sacred erotic rapture:

(1) renunciates who are excessively inclined to asceticism,
(2) others who are unable to distinguish between mundane sexuality and the divine eros, and
(3) those who, though devotees, are indifferent to the erotic mysticism of the Bhāgavata-purāṇa.

Since the subject is esoteric and rather difficult to understand, as well as being expansive, I have only given an abbreviated description of it here.