Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 19
Sanskrit:
श्रीभगवानुवाचन वै शूरा विकत्थन्ते दर्शयन्त्येव पौरुषम् ।न गृह्णीमो वचो राजन्नातुरस्य मुमूर्षत: ॥ १९ ॥
ITRANS:
śrī-bhagavān uvācana vai śūrā vikatthantedarśayanty eva pauruṣamna gṛhṇīmo vaco rājannāturasya mumūrṣataḥ
Translation:
The Supreme Lord said: Real heroes do not simply boast but rather show their prowess in action. We cannot take seriously the words of one who is full of anxiety and who wants to die.