Shiva Purana
अन्ये च ये समुत्पन्ना यथानुक्रमतो लयम् ॥ यांति नैव तथा रुद्रः शिवे रुद्रो विलीयते ॥ ४३ ॥
Other beings and gods who are born get dissolved in due order but not so Rudra. Rudra gets merged in Śiva.
english translation
anye ca ye samutpannA yathAnukramato layam ॥ yAMti naiva tathA rudraH zive rudro vilIyate ॥ 43 ॥
hk transliteration by Sanscript