अयं स्वभावः स्वत एव यत्पर -श्रमापनोदप्रवणं महात्मनाम् ।सुधांशुरेष स्वयमर्ककर्कश -प्रभाभितप्तामवति क्षितिं किल ॥ ४० ॥
In plain words
It is simply their nature — great souls turn, on their own, toward easing what wearies other people. Just as the moon, without being asked, soothes the earth after it has been scorched raw by the sun's harsh light.
Close to the Sanskrit
This is the nature, spontaneously indeed, of great souls — [a nature] inclined to remove the fatigue of others. This moon, of itself, indeed cherishes the earth scorched by the harsh light of the sun.