If one knew oneself to be precious
One would guard oneself with care.
The sage will watch over herself
In any part
Of the night.

In first establishing himself
In what is proper
And only then teaching others,
The sage will not be stained.

The sage, or spiritual teacher must care for himself, protect himself, and develop spiritually first, before he can teach others.  Otherwise, like many preachers today, he is speaking in theory only, with no personal knowledge.
I believe the phrase "In any part of the night" means in the world of darkness and the dark beings, demons and devils, that dwell there.  When you are developing spiritually, you must watch out for them and take precautions to avoid them.