Kautilya's Arthashastra 7.5.47

7.5.47

jyāyastve cāpi labdhārthaḥ samo 'pi parikalpate /
abhyuccitaś cāviśvāsyo vṛddhiś cittavikāriṇī //

Though actuated with feelings of true friendship, the conqueror has reason to fear his ally, though of equal power, when the latter attains success in his mission; having succeeded in his mission, an ally of equal power is likely to change his attitude even towards the conqueror of superior power.

An ally of superior power should not be relied upon, for prosperity changes the mind. Even with little or no share in the spoils, an ally of superior power may go back, appearing contented; but some time afterwards, he may not fail to sit on the lap of the conqueror and carry off twice the amount of share due to him.