Shiva Purana
सुनिर्देशाद्ब्रह्मणो हि सस्त्रीकः पुत्रकाम्यया ॥ स त्र्यक्षकुलनामानं ययौ च तपसे गिरिम् ॥ ३ ॥
At the direction of Brahmā he went to the mountain Ṛkṣakula accompanied by his wife in order to perform penance there, with the desire to get son.
english translation
sunirdezAdbrahmaNo hi sastrIkaH putrakAmyayA ॥ sa tryakSakulanAmAnaM yayau ca tapase girim ॥ 3 ॥
hk transliteration by Sanscript