In this verse (SB 4.6.37) it is specifically mentioned that he was speaking to the great sage Narada, a celebrated devotee. Narada was asking Lord Siva about devotional service, and Siva, being the topmost Vaisnava, was instructing him

Expressions researched:
"In this verse it is specifically mentioned that he was speaking to the great sage Nārada, a celebrated devotee. Nārada was asking Lord Śiva about devotional service, and Śiva, being the topmost Vaiṣṇava, was instructing him"

Srimad-Bhagavatam

SB Canto 4

The lord was sitting on a mattress of straw because such a sitting place is accepted by persons who are practicing austerities to gain understanding of the Absolute Truth. In this verse it is specifically mentioned that he was speaking to the great sage Nārada, a celebrated devotee. Nārada was asking Lord Śiva about devotional service, and Śiva, being the topmost Vaiṣṇava, was instructing him.

SB 4.6.37, Translation and Purport

He was seated on a straw mattress and speaking to all present, including the great sage Nārada, to whom he specifically spoke about the Absolute Truth.

The lord was sitting on a mattress of straw because such a sitting place is accepted by persons who are practicing austerities to gain understanding of the Absolute Truth. In this verse it is specifically mentioned that he was speaking to the great sage Nārada, a celebrated devotee. Nārada was asking Lord Śiva about devotional service, and Śiva, being the topmost Vaiṣṇava, was instructing him. In other words, Lord Śiva and Nārada were discussing the knowledge of the Veda, but it is to be understood that the subject matter was devotional service. Another point in this connection is that Lord Śiva is the supreme instructor and the great sage Nārada is the supreme audience. Therefore, the supreme subject matter of Vedic knowledge is bhakti, or devotional service.