分別功德論 4.3

4.3

優陀夷比丘勸導以為最。比丘皆勸導，所以稱最者，佛將還度本國，先遣現神變。與王相酬酢，一一解釋，人所度不可計，故稱勸導最也。

The monk Udāyin was supreme in exhorting and guiding. All monks exhort and guide; why is he declared supreme? When the Buddha was about to return to deliver his home country, he first sent him ahead to display miraculous transformations. Engaging in conversation with the king, he explained things one by one; those whom he delivered were countless, and therefore he is declared supreme in exhorting and guiding.