Matsyapurana 101.4

101.4

yastvekabhaktena samāṃ śivaṃ haimavṛṣānvitam
dhenuṃ tilamayīṃ dadyāt sa padaṃ yāti śāṃkaram
etadrudravrataṃ nāma pāpaśokavināśanam //

The devotee keeping up the (2) Rudra-Vrata should, for a year, have only one meal a day, after which he should give away one bull of gold and a cow of sesamum. This observance is also the destroyer of ills and helps the devotee to go to the region of Śiva, and raises him to the rank of Śiva.—4.