Kautilya's Arthashastra 7.5.46

7.5.46

sattrād apasared yattaḥ kalatram apanīya vā /
samād api hi labdhārthād viśvas tasya bhayaṃ bhavet //

Till his discharge, the good conduct of an ally of usually bad character should be closely scrutinised either by suddenly coming out at a critical time from a covert position (sattra) to examine his conduct, or by having his wife as a pledge for his good conduct.

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.