Shiva Purana
तथैनां च तदा दृष्ट्वा नायान्तीह समीपगाः ॥ अत्रेश्च तपसश्चैवानसूया शिवसेवनम् ॥ २२॥
O leading brahmins, Anasūyā’s service to Śiva performed sacredly through mind, speech and body surpassed even the penance of Atri.
english translation
tathainAM ca tadA dRSTvA nAyAntIha samIpagAH ॥ atrezca tapasazcaivAnasUyA zivasevanam ॥ 22॥
hk transliteration by Sanscript