These two sages, Nara and Nārāyaṇa, were the direct personal forms of the Supreme Lord. When Mārkaṇḍeya Ṛṣi saw Them, he immediately stood up and then with great respect offered Them obeisances by falling down flat on the ground like a stick.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
ते वै भगवतो रूपे नरनारायणावृषी । दृष्ट्वोत्थायादरेणोच्चैर्ननामाङ्गेन दण्डवत्
te vai bhagavato rūpe naranārāyaṇāvṛṣī | dṛṣṭvotthāyādareṇoccairnanāmāṅgena daṇḍavat
SB 12.8.35