Valmiki Ramayana Kishkindha Kanda Sarga 51 Shloka 12
Original Shlokaस तु वर्षसहस्राणि तपस्तप्त्वा महावने।।4.51.12।। पितामहाद्वरं लेभे सर्वमौशनसं धनम्।
1 source checked for this shloka
सः that, वने in the forest, वर्षसहस्राणि for thousands of years, महावने dense forest, तपः penance, तप्त्वा having performed, पितामहात् from the creator Brahma, वरम् boon, औशनसम् of Usanas, सर्वम् all, धनम् wealth, लेभे inherited.
'He (Maya) performed rigorous penance in the dense forest for thousands of years seeking the favour of Brahma, the creator and obtained a boon that he should inherit all the wealth of Usanas (Shukra).