Why did he not sit among jesters?
Radak: Your word is the Simchah of my heart, i.e. of the intellect. Other Simchah, i.e. of the body, was not Simchah [for me], that I would sit among them when they jest and be happy with them. Rather, I sat alone, isolated in my house.
Malbim: I did not seek Simchah to bring Nevu'ah on myself 1 , for Your Nevu'ah was of anger and punishments.
How would this bring Nevu'ah? Shechinah does not rest on someone amidst laughter or frivolity, only amidst Simchah of Mitzvah (Pesachim 117a)! (PF)
Why does it say "Mipnei Yadcha"?
Rashi: Due to Nevu'ah, which came from You. Radak - this is like "Haysah Alai Yad Hashem" (Yechezkel 37:1). Also Yonason translates like this.
Radak: Due to Your striking. This is like "Yad Hashem Hoyah" (Shemos 9:3).
Malbim: Refer to 15:17:1:2.
Why did he say "Badad Yashavti"?
Rashi: I sat alone, stunned in Aveilus, for Nevu'ah of anger filled me, of Churban of Your Bayis.
What is the meaning of "Za'am Mileisani"?
Radak citing Targum Yonasan: Nevu'ah of curses filled me.
