SB 3.12.16

rudrāṇāṁ rudra-sṛṣṭānāṁ
 samantād grasatāṁ jagat
niśāmyāsaṅkhyaśo yūthān
 prajāpatir aśaṅkata
Word for word: 
rudrāṇām — of the sons of Rudra; rudra-sṛṣṭānām — who were generated by Rudra; samantāt — being assembled together; grasatām — while devouring; jagat — the universe; niśāmya — by observing their activities; asaṅkhyaśaḥ — unlimited; yūthān — assembly; prajā-patiḥ — the father of the living entities; aśaṅkata — became afraid of.
Translation: 
The sons and grandsons generated by Rudra were unlimited in number, and when they assembled together they attempted to devour the entire universe. When Brahmā, the father of the living entities, saw this, he became afraid of the situation.
Purport: 

The generations of Rudra, the incarnation of anger, were so dangerous to the maintenance of universal affairs that even Brahmā, the father of the living entities, became afraid of them. The so-called devotees or followers of Rudra are also a menace. They are sometimes dangerous even to Rudra himself. Descendants of Rudra sometimes make plans to kill Rudra — by the grace of Rudra. That is the nature of his devotees.