Valmiki Ramayana Bala Kanda Sarga 63 Shloka 16
Original Shlokaआमन्त्रयन् समागम्य सर्वे सर्षिगणा स्सुरा:। महर्षिशब्दं लभतां साध्वयं कुशिकात्मज:।।1.63.16।।
1 source checked for this shloka
सर्षिगणा: along with hosts of rishis, सर्वे all, सुरा: devatas, समागम्य having met together, अयम् कुशिकात्मज: this Viswamitra, साधु rightly, महर्षिशब्दम् title of Maharshi, लभताम् be obtained, आमन्त्रयन् thought over.
After consultations the gods and sages decided that this son of Kushika (Viswamitra) deserved the status of a Maharshi".