Shiva Purana
लिंगमूर्तिर्महेशस्य शिवस्य परमात्मनः ॥ स्नानकाले प्रकुर्वीत जयशब्दादिमंगलम् ॥ ३९ ॥
Linga is the embodiment of Lord Maheśa, Lord Śiva, the Supreme Soul. At the time of bathing one should chant the auspicious words Jaya and others.
english translation
liMgamUrtirmahezasya zivasya paramAtmanaH ॥ snAnakAle prakurvIta jayazabdAdimaMgalam ॥ 39 ॥
hk transliteration by Sanscript