大方廣佛華嚴經疏 49.29

49.29

第七降雨滋榮喻，喻歡喜聲，稱根增長故。離佛無聲，不從外來；離機無聲，不從內出。

Seventh, the analogy of falling rain nourishing growth illustrates the joyful voice, because it causes growth in accordance with capacities. Apart from the Buddha there is no voice, so it does not come from without; apart from capacities there is no voice, so it does not issue from within.