四分律刪補隨機羯磨 2.176

2.176

(In the Vinaya: "There was a bhikṣu who intended to enter the earlier retreat on the sixteenth day of the fourth month, but had not arrived at his dwelling place and only reached it on the seventeenth day. The Buddha said: 'Observe the later retreat.'" One should follow the text above, saying "the summer retreat for the later three months"; the rest of the text is as above. In this way, up to the sixteenth day of the fifth month, the procedure for the later retreat follows the above.)