CC Ādi 5.105

rudra-rūpa dhari’ kare jagat saṁhāra
sṛṣṭi-sthiti-pralaya — icchāya yāṅhāra
Synonyms: 
rudra-rūpa — the form of Lord Śiva; dhari’ — accepting; kare — does; jagat saṁhāra — annihilation of the material world; sṛṣṭi-sthiti-pralaya — creation, maintenance and annihilation; icchāya — by the will; yāṅhāra — of whom.
Translation: 
Assuming the form of Rudra, He destroys the creation. Thus creation, maintenance and dissolution are created by His will.
Purport: 

Maheśvara, or Lord Śiva, is not an ordinary living being, nor is he equal to Lord Viṣṇu. Effectively comparing Lord Viṣṇu and Lord Śiva, the Brahma-saṁhitā says that Viṣṇu is like milk, whereas Śiva is like yogurt. Yogurt is nothing like milk, but nevertheless it is milk also.