«فُلَانٌ يَتَكَلَّمُ بِالدُّرَرِ»
So-and-so speaks in pearls—that is, with exceptionally fine and valuable words.
Literal sense: precious pearls.
Intended sense: excellent, elegant utterances.
Relation: resemblance in beauty and value.
Indicator: the verb «يَتَكَلَّمُ»; ordinary speaking does not produce physical pearls.
Similarity permits the transfer, while the context makes the figurative interpretation appropriate.