Shloka 19
Chapter 81: Trust, Allies, and the Qualifications of the King’s Artha-Secretary (अर्थसचिव)
क्षताद् भीतं विजानीयादुत्तमं मित्रलक्षणम् | ये तस्य क्षतमिच्छन्ति ते तस्य रिपव: स्मृता:
kṣatād bhītaṃ vijānīyād uttamaṃ mitralakṣaṇam | ye tasya kṣatam icchanti te tasya ripavaḥ smṛtāḥ ||
毗湿摩说道：应当把这样的人视为真友的最高标志——一想到盟友将遭受伤害或损失，便心生惶惧。凡希求其受害者，皆当记为其敌。在王道之中，朋友乃是那种人：尤其在法（dharma）之事上，恒常竭力护持君王免于衰败；及至兴盛来临，又随其所能，助长其福祉。
भीष्म उवाच
Educational Q&A
A true friend is defined by protective concern: he fears the king’s (or ally’s) loss as his own and actively works to prevent harm, especially in dharmic affairs. Whoever wishes the ruler’s damage is, by that intention, an enemy.
In the Shanti Parva’s instruction on rājadharma, Bhishma advises Yudhishthira on how to judge allies and opponents. He gives a practical ethical criterion: the friend is the one who is anxious about your welfare and guards you from decline; those who seek your ruin are to be treated as foes.