Shiva Purana
मदात्मकमिदं नित्यं मम सान्निध्यकारणम् । महत्पूज्यमिदं नित्यमभेदाल्लिंगसिंगिनोः ४३ ।
The phallic symbol and the symbolised Śiva are non-different. Hence this phallic emblem is identical with me. It brings devotees quite near to me. It is worthy of worship therefore.
english translation
madAtmakamidaM nityaM mama sAnnidhyakAraNam । mahatpUjyamidaM nityamabhedAlliMgasiMginoH 43 ।
hk transliteration by Sanscript