四分律刪繁補闕行事鈔 2.232

2.232

The Samantapāsādikā states: When many bhikṣus and one śrāmaṇera travel together, the bhikṣus carry their own food; when the time arrives, they divide it among themselves. Having divided it, the śrāmaṇera says to a bhikṣu: 'I take my share and exchange it with the venerable one.' Having exchanged it, he exchanges it again with the second bhikṣu, down to the junior seat. If the śrāmaṇera does not understand, the bhikṣu personally brings the food to give him and teaches him to exchange it together, and there is no transgression (there is no leftover overnight food, illicit touch, etc.). Further, when carrying rice while traveling, if the śrāmaṇera is young, the bhikṣu may prepare the rice, but must not light the fire. When it boils, he must not blow on it or stir it, which would incur a duṣkṛta. Once cooked, it is divided as above; exchanging it sequentially is permitted. (By standard doctrinal reasoning, if one currently eats leftover food and gives it to a layperson, if it is passed along to others, it is impure due to illicit touch, because the mind has not relinquished attachment, making it impure.)
The Daśādhyāya-vinaya states: A bhikṣu passes food to a śrāmaṇera, the śrāmaṇera passes bowl and food to the bhikṣu, and the bhikṣu washes his hands and receives it anew; because he genuinely gave it to the śrāmaṇera with single-minded intent, it is pure. When traveling far to places where food is hard to find, a bhikṣu is permitted to carry food himself and exchange it with others for pure food. Nowadays there are those who directly give food to a kappiyakāraka and immediately beg it back from him; neither of them genuinely gives or receives, so it is not called valid exchange (the method in the Samantapāsādikā is preferable).
A bhikṣu instructed a śrāmaṇera to hold his bowl; after the śrāmaṇera ate, he brought the impure bowl to the master. The Buddha said: 'Without urgent business, one should not instruct a śrāmaṇera to hold one's bowl; if instructing him to hold it, one must receive it anew from the śrāmaṇera.'