Shiva Purana
अभिमंत्र्य ततस्तस्मिन्धेनुमुद्रां प्रदर्शयेत ॥ शंखमुद्रां च तेनैव प्रोक्षयेदस्त्रमंत्रतः ॥ ७ ॥
After chanting the mantra one should then present the cow mudra to the deity Sprinkle the conchshell and mudra with the same water, chanting the mantra Astra.
english translation
abhimaMtrya tatastasmindhenumudrAM pradarzayeta ॥ zaMkhamudrAM ca tenaiva prokSayedastramaMtrataH ॥ 7 ॥
hk transliteration by Sanscript