SB 4.6.42

brahmovāca
jāne tvām īśaṁ viśvasya
 jagato yoni-bījayoḥ
śakteḥ śivasya ca paraṁ
 yat tad brahma nirantaram
Synonyms: 
brahmā uvāca — Lord Brahmā said; jāne — I know; tvām — you (Lord Śiva); īśam — the controller; viśvasya — of the entire material manifestation; jagataḥ — of the cosmic manifestation; yoni-bījayoḥ — of both the mother and father; śakteḥ — of potency; śivasya — of Śiva; ca — and; param — the Supreme; yat — which; tat — that; brahma — without change; nirantaram — with no material qualities.
Translation: 
Lord Brahmā said: My dear Lord Śiva, I know that you are the controller of the entire material manifestation, the combination father and mother of the cosmic manifestation, and the Supreme Brahman beyond the cosmic manifestation as well. I know you in that way.
Purport: 

Although Lord Brahmā had received very respectful obeisances from Lord Śiva, he knew that Lord Śiva was in a more exalted position than himself. Lord Śiva’s position is described in Brahma-saṁhitā: there is no difference between Lord Viṣṇu and Lord Śiva in their original positions, but still Lord Śiva is different from Lord Viṣṇu. The example is given that the milk in yogurt is not different from the original milk from which it was made.