四分律行事鈔資持記 2.1176

2.1176

五十。空中不成，謂能受在空；若論所對在空，亦應不成；故知能所俱須在地。如前即指第二門。

"Fifty: unaccomplished in the air" means that the capable recipient is in the air; if we consider the object counterpart being in the air, it should also be unaccomplished; thus we know that both the agent and the object must be on the ground. "As before" refers to the second section.