Skandapurana 5.151.15

5.151.15

kṛṣṇārjunau tadā martye dvāparāṃte dvijottamāḥ ..
avatīrṇo dharāpṛṣṭhe mithaḥ snehānugau tadā ..
naranārāyaṇāvetau svayameva vyavasthitau .. 15 ..

At that time, at the end of the Dvāpara age, O best of the twice-born, Kṛṣṇa and Arjuna / descended onto the surface of the earth, united by mutual affection; / these two, Nara and Nārāyaṇa, were stationed there in person.