| Quote #1
Where thoughts serenely sweet express (line 11)
The sound of this line, with its repeated s sound (a.k.a. "sibilance"), reflects the meaning of the line as well: the line sounds as soothing and "serene" as her thoughts supposedly are.
| Quote #2
How pure, how dear their dwelling place. (line 12)
The speaker assumes that the calm and "serene" expression on the woman's face reflects the "pur[ity]" of her mind.
| Quote #3
But tell of days in goodness spent, (line 16)
The speaker also assumes that the woman's sweet expression "tell[s]" the story of her past goodness – that's a lot to read just from someone's facial expression.