Bhagavad Gita Chapter 11.50
ity arjunaḿ vāsudevas tathoktvā
svakaḿ rūpaḿ darśayām āsa bhūyaḥ
āśvāsayām āsa ca bhītam enaḿ
bhūtvā punaḥ saumya-vapur mahātmā
Sanjaya said to Dhritarashtra: The Supreme Personality of Godhead, Krishna, having spoken thus to Arjuna, displayed His real four-armed form and at last showed His two-armed form, thus encouraging the fearful Arjuna.