大方廣佛華嚴經隨疏演義鈔 61.37

61.37

疏「如淨鑑止水」者，欲惡如泥，初禪之定如淨動水。今無欲惡復滅覺觀，如淨止水。是則初禪慶其所離；此慶所得，得亡照故。

Regarding the commentary's "like a clear mirror and still water": desire and evils are like mud; the concentration of the first dhyāna is like clear, moving water. Now, devoid of desire and evils and having further extinguished vitarka and vicāra, it is like clear, still water. Thus, the first dhyāna rejoices in what it has left behind; this [second dhyāna] rejoices in what it has attained, because it attains the fading of illumination.