In “Lī min fulān ṣadīq ḥamīm,” “lī” relates the statement to the speaker, “min fulān” names the source of extraction, and “ṣadīq ḥamīm” provides the rhetorically extracted figure. The audience holds both in mind.
Important distinction: Min alone does not create tajrīd. “Akhadhtu min fulān kitāban” (I took a book from him) describes an actual transfer, whereas tajrīd concerns an imagined extraction meant to intensify a quality.
The proper test is not merely which particle occurs; it is whether the second figure is an imagined counterpart possessing the same relevant attribute.