Why does it mention that David took more wives?
'Rashi': This shows his strength.
What is the difference between a wife and a Pilegesh?
Refer to Shoftim 8:31:1:1,2 and the notes there. A wife has Kidushin and Kesuvah.
Here it says that David married other wives. Why does it say in Shmuel II, 5:13 wives and concubines?
Abarvenel (Shmuel II, 5:13): Because a concubine has Kidushin, she is called a wife. Malbim (ibid.) ? this opinion can say that here they are called concubines because they do not have Kesuvah.
Chomas Anach: It is for the honor of David. There it mentions concubines first, for this was a Chidush. Only now that he became king [over all Yisrael], he was permitted to take concubines, like the Rambam says.
