Shiva Purana
पुत्रार्थे पार्थिवी मूर्त्ति शैवी दशरथो हि सः ॥ समानर्च विशेषेण वसि ष्ठस्याज्ञया मुनेः ॥ ३१॥
At the behest of the sage Vasiṣṭha, Daśaratha particularly worshipped the earthen idol of Śiva for obtaining sons.
english translation
putrArthe pArthivI mUrtti zaivI dazaratho hi saH ॥ samAnarca vizeSeNa vasi SThasyAjJayA muneH ॥ 31॥
hk transliteration by Sanscript