Kautilya's Arthashastra 7.9.44

7.9.44

mitrabhāvād dhruvaṃ mitraṃ śatrusādhāraṇāc calam /
na kasyacid udāsīnaṃ dvayor ubhayabhāvi tat //

whoever is of an amicable nature is a true friend; whoever sides also with the enemy is a mutable friend and whoever is indifferent to neither (the conqueror and his enemy) is a friend to both;