Kautilya's Arthashastra 7.7.18

7.7.18

jātavyasanaprakṛtirandhram anekaviruddham anyato labhamāno vā samo balasamādd hīnena lābhena paṇeta //

When a king of equal power, capable of receiving the help of an army from another quarter requests of another king in troubles due to the diminished strength of the elements of sovereignty, and with many enemies, the help of the latter's army in return for the payment of a share in the profit less than the strength of the army supplied deserves, the latter, if powerful, may declare war or accept the terms otherwise.