Having seen the impenetrable Vyuha formed by Bhishma and having concluded it to be really impenetrable, the king became pale and he thus spoke to Arjuna.
व्यूह भीष्मेण चाभेद्यं कल्पितं प्रेक्ष्य पाण्डवः। अभेद्यमिव सम्प्रेक्ष्य विवर्णोऽर्जुनमब्रवीत्॥