What's up with Ulysses S. Grant's father-in-law giving him a slave?

IIUC, there was tension between Grant's family and his in-laws because the Grants were outspoken abolitionists and the Dents were prominent slave-keepers.

When Grant was at some low point, near to destitute, father-in-law gave him a slave. Which Grant then freed when he could have sold the poor man and pocketed a fortune.

On the surface, the gift (to Grant) seems generous on Dent's part, but on like two seconds of thought it seems passive-aggressive and plainly just shitty. One can imagine the father-in-law giving Grant the slave with the aim of inducing him to betray his abolitionist principles, which no doubt would have been a source of great amusement to the Dents.

And anyway you can imagine Dent being outraged at Grant setting the man free.

Do we have any background on what passed between Grant and Dent around this incident? Anything about the nature of their relationship, what Dent hoped to achieve, and how, if at all, Grant's response affected the relationship?