1)
What is the meaning of "leva'Avor Sabev"?
1.
Rashi: it is in order to cause [the matter of David's son to be clarified].
2)
What was David's Chachmah?
1.
Rashi: He knew that Yo'av instructed her.
2.
Radak: He knows both matters pertaining to himself, and to other matters.
