Mbh 1.3.9b

And his preceptor observing that he was still fat, said again unto him, ‘Upamanyu, my child, I take from thee all thou obtainest in alms and thou dost not go a-begging a second time, and yet art thou in healthy condition. How dost thou support thyself?’ And Upamanyu, thus questioned, answered, ‘Sir, I now live upon the milk of these cows.’ And his preceptor thereupon told him, ‘It is not lawful for thee to appropriate the milk without having first obtained my consent.’ And Upamanyu having assented to the justice of these observations, went away to tend the kine. And when he returned to his preceptor’s abode, he stood before him and saluted him as usual. And his preceptor seeing that he was still fat, said, ‘Upamanyu, my child, thou eatest no longer of alms, nor dost thou go a-begging a second time, not even drinkest of the milk; yet art thou fat. By what means dost thou contrive to live now? And Upamanyu replied, ‘Sir, I now sip the froth that these calves throw out, while sucking their mother’s teats.’ And the preceptor said, ‘These generous calves, I suppose, out of compassion for thee, throw out large quantities of froth. Wouldst thou stand in the way of their full meals by acting as thou hast done? Know that it is unlawful for thee to drink the froth.’ And Upamanyu, having signified his assent to this, went as before to tend the cows. And restrained by his preceptor, he feedeth not on alms, nor hath he anything else to eat; he drinketh not of the milk, nor tasteth he of the froth!