Shiva Purana
तथा स्वकर्मणैकेन प्ररोहमुपयांति वै ॥ ब्रह्मा विष्णुश्च रुद्राश्च स शिवः परिगीयते ॥ ३०॥
They spring up through their own action. Śiva manifests himself as Brahmā, Viṣṇu and Rudra.
english translation
tathA svakarmaNaikena prarohamupayAMti vai ॥ brahmA viSNuzca rudrAzca sa zivaH parigIyate ॥ 30॥
hk transliteration by Sanscript