«أَيْنَ أَنْتَ مِنَ الْبَيْتِ النَّادِرِ الْجَامِعِ مُشَبَّهَاتِ الثَّغْرِ؟»
What do you know of the rare verse combining images for the teeth?
Thaghr often refers to the front teeth or the smiling mouth. The speaker claims that a more exceptional verse combines several comparison-images for that feature.
He is proposing breadth of imagery as a mark of poetic brilliance; whether accumulation always improves poetry remains a separate matter.