The previous sentence of the lingering skylight and cloud shadow is: Half an acre of square pond is opened.
This is a poem from "Looking at Books and Feelings" written by Zhu Xi, a scholar in the Song Dynasty.
The whole poem "Impressions after Reading the Book" is as follows:
As soon as the half-acre square pond opens, the skylight and cloud shadows linger.
Ask him how clear it is? Come for living water from a source.