Maha Prajnaparamita 21.1:
In the Maha Prajnaparamita Sutra, the god Shakra appears and scatters flowers before Subhuti. When Subhuti asks why he is doing this, Shakra says he is making offerings to thank Subhuti for teaching him about prajna. Subhuti replies, “But I have not said one word. How can you say I teach prajna?” To this, Shakra replies, “So it is. The venerable Subhuti does not teach, and I do not hear any dharma. Nothing taught and nothing heard. This is true prajna.”