Kautilya's Arthashastra 7.7.20

7.7.20

evaṃbhūto vā samaḥ sāmantāyattakāryaḥ kartavyabalo vā balasamād viśiṣṭena lābhena paṇeta //

When a king who is under troubles, who has his works at the mercy of his neighbouring kings, and who has yet to make an army, requests of another king of equal power the help of the latter's army in return for the payment of a share in the profit greater than the strength of the army supplied deserves, the latter may accept the terms if the proposer is of good intentions: but otherwise war may be declared.