四分律行事鈔資持記 2.759

2.759

十六。（佛在舍衛，跋難陀得羊毛貫杖頭行，招譏故制。）名云過限者，出三由旬故。

Sixteen. (The Buddha was in Śrāvastī. Upananda obtained sheep's wool, strung it on the tip of a staff, and walked along, inviting criticism; hence it was prohibited.) The name says "exceeding the limit" because it exceeds three yojanas.