Heaven and earth do not fixate on benevolent; they deal with all things as if they are grass dogs.

The sages do not fixate on benevolent; they deal with people as if they are grass dogs.

-> Sun and moon rises and falls impartially, they do not shine over certain country or people just because they like them more.  Similarly, enlightened sages who transcend the self has no bias and deal with all according to the natural rhythm of the universe

If we look at the space between heaven and earth, isn’t it like a musical wind chamber?

When emptied it is without limit, when moved it gives out limitlessly.

-> Multiple levels of interpretation are possible here. On breathing its describe the natural coming and going of air or energy in one’s body. On awareness, it describes the coming and going of consciousness in one’s life, on the universal level, it describes the coming and going of universe with one’s perception.

Excessive speeches exhaust ones reasons, it is better to stay centered.

-> it is easy to get lost in words and thoughts. Seek and abide in the center, which is the underlying reality beneath speeches and reasons.

* * *

Chapter 5 Discussion:

We have biases. We like certain people better, we don’t like others. We prefer certain situation (e.g. chocolate), we do not prefer others (bitterness). Yet, when we look around the nature, the sky (including the sun and moon and stars), does not have bias and shine only to certain people or country. The earth beneath and supporting us all, does not favor certain species other others. They treat us all equal like neutral grass dogs, and continue its role and jobs as sky and earth. Through this lack of bias, impartiality is achieved.  A realized sage, similarly, also live ones life like heaven and earth, beyond the limitation of any bias, and therefore achieve impartiality. The way towards this impartiality and its effects (benefits) will be explained more in Chapter 16.

DDJ Chapter 5 bilingual text: https://www.lisiming.net/philosophy/chinese-philosophy/daoist/daoist-philosophy/dao-de-jing-core-33-chapters/ddj1-8/