Shiva Purana
ब्राह्मणैः क्षत्रियैर्वैश्यैः शूद्रै रपि च संस्करैः । अपभ्रंशैर्धृतं भस्मत्रिपुंड्रोद्धूलनात्मना १२ ।
By Brahmins, Kshatriyas, Vaishyas, and even Shudras, with their respective rituals, the Tripundra is worn, and by cleansing the body with ashes, it is firmly upheld, preserving its sanctity.
english translation
brAhmaNaiH kSatriyairvaizyaiH zUdrai rapi ca saMskaraiH । apabhraMzairdhRtaM bhasmatripuMDroddhUlanAtmanA 12 ।
hk transliteration by Sanscript