Shiva Purana
परिधाय शुभं वस्त्रमन्तर्वासश्शुभन्तथा॥ आचम्य च त्रिवारं हि पूजारंभं समाचरेत् ॥ ३३॥
The undercloth and the usual cloth shall be pure. The devotee shall perform the Ācamana thrice and begin worship.
english translation
paridhAya zubhaM vastramantarvAsazzubhantathA॥ Acamya ca trivAraM hi pUjAraMbhaM samAcaret ॥ 33॥
hk transliteration by Sanscript