Shiva Purana
शुद्धप्रदेशसंभूतां मृदमाहृत्य यत्नतः । शिवलिंगं प्रकल्पेत सावधानतया द्विजाः ६ ।
O brahmins, he shall bring clay from a clean place and carefully make the phallic image.
english translation
zuddhapradezasaMbhUtAM mRdamAhRtya yatnataH । zivaliMgaM prakalpeta sAvadhAnatayA dvijAH 6 ।
hk transliteration by Sanscript