僧羯磨 1.211

1.211

及界法（時諸比丘往安居處欲安居，入界便明相出，彼有疑，為成安居不？佛言：「若為安居故來，便成安居。」次入園亦同；次一脚入界、入園，亦如是。）

Reaching the Boundary Procedure (At that time, bhikṣus went to the retreat place wishing to enter the rains retreat, and dawn broke just as they entered the boundary. They had doubts as to whether the rains retreat was completed or not. The Buddha said: "If they came for the sake of the rains retreat, the rains retreat is completed." Entering the monastery garden next is also the same; having one foot inside the boundary or entering the monastery garden is likewise.)