1)
What is "Cherpasi"?
1.
Rashi: It is his insult to me - "ha'Yom Rabu Avadim ha'Mispartzim" (verse 10). Radak - and "who is David and who is Ben Yishai"?
2)
For how many things did David bless Hashem?
1.
Malbim: It was for three. (a) He punished Naval for insulting him. (b) He prevented David from taking vengeance by himself. (c) He punished Naval also for his other Aveiros 1 ; it was not only due to David. If someone is punished due to Ploni, Ploni does not enter Hashem's abode (Shabbos 149b).
1
Malbim did not explain how David knew this.