a) by Ben Jonson and b) by a concealed "pretty wit",
the True Shakespeare!
Epigram nr. 147/126 ("B.J. approbation of a copy of verses." 1640/1641, in sonnet form) is ambiguous and fully understandable only when you consider the Shakespeare Authorship Secret.
In this Epigram the author is complaining about Ben Jonson. The author describes himself as a witty "gentleman" who once showed Ben Jonson some of his own verses of "a tragick sense".-
He calls Jonson a tacit accomplice in the handling of his verse ("a kind partaker") since he clearly knew who wrote the lines ("he needs must know the maker"), but Jonson was unfair ("What unjust man he was") because he "advanced his rime"(Madrigal) as his own.- NO! says the author, to Jonson, this poem was his, it belonged to the one who's held a pretty wit.
B.) Why was Jonson a "kind partaker of the sad lines"?
The author most likely refers to the poem ("Madrigal", "On a Lovers dust made sand for an hour-glass). Ben Jonson at the very day of his departure January 19th-1619 after his visit in Edinburgh presented to the Poet William Drummond together with a Hand written dedication " ....I Ben Jonson (....) have with mine own Hand, to satisfy his request, written this Imperfect song." (Reference).