Valmiki Ramayana Bala Kanda Sarga 63 Shloka 1

वर्षसहस्रे when thousand years, पूर्णे had been completed, सर्वे all, सुरा: devatas, तप: फलचिकीर्षव: desiring to bestow the fruits of his austerities, व्रतस्नातम् who had taken the ritual bath after completion of the ritual, महामुनिम् mighty ascetic, अभ्यागच्छन् approached.

All the gods wanted to bestow the fruits of austerties on the mighty ascetic (Viswamitra). They approached him after a thousand years of penace and his final ritual bath. Viswamitra obtains the title of Maharshi -- Menaka creates impediments to his penance -- Viswamitra performs intense austerities to obtain the rank of Brahmarshi.