Illustrations paragraph 6
6. Now we will go back and explain what we allowed at the start of section 4. If the groom has very serious faults, there is a difference between the kinds of faults.
If the fault is a physical illness, and the bride's father does not know about it because it is an internal illness that cannot be seen from the outside, it is clear that there is no ban of rechilus in telling him (if all the details are met).
There is another case where he must tell him: if it is heard about the groom that he holds heretical views (apikorsus), Heaven forbid. He must tell him. About this the verses were placed next to each other: "Do not go as a talebearer among your people" and "Do not stand by your fellow's blood."
But if the fault is that the groom has little Torah knowledge, he does not need to tell him. The bride's father caused the loss to himself: he should have brought the groom to Torah scholars to test how much Torah he knows. Since he did not do so, he accepted the groom as he is.