What did he mean when Bil'am said "Mah Ekov Lo Kaboh Keil"?
Rashi: a. With reference to Ya'akov, whom Hashem called 'Eil', 1 Bil'am meant that even when they deserved to be cursed, Ya'akov did not curse them, only their anger; 2 b. when their father Ya'akov tricked his father into blessing him and deserved to be cursed, he concluded "Gam Baruch Yihyeh!" 3 and c. In connection with the B'rachos and K'lalos on Har Gerizim and Har Eival, by those who blessed, it says "Eileh Ya'amdu Levarech es ha'Am" 4 , whereas by those who cursed it says (not, 've'Eileh Ya'amdu Lekalel', but) "ve'Eileh Ya'amdu al ha'Kelalah." 5
What was he referring to when he said "Mah Ez'om Lo Za'am Hashem"?
Rashi (citing Sanhedrin 105b): He was referring to his one strength - the ability to pinpoint the moment that Hashem was angry 1 each day, but Hashem had not been angry throughout the period that he attempted to curse Yisrael. 2
Rashbam: 'How can I bring upon them Hashem's anger when Hashem has not been angry with them?'
Targum Onkelos: 'How can I drive them out when Hashem has not driven them out?'
Targum Yonasan: 'How can I decrease them when Hashem has promised to increase them?'
Rashi writes that Bil'am could pinpoint the moment of Hashem's anger [to curse them then]. The moment is the time to say 'Rega', only about a 16th of a second (Brachos 7a)! What curse could he say in such a short time?
Da'as Zekenim #1, Hadar Zekenim (22:41) #1, Rosh (22:33): He could say 'Kalem' (finish them off)! Hashem reversed it to Melech ("u'Sru'as Melech Bo"
Da'as Zekenim, Hadar Zekenim: This is difficult, for the Brachos reveal what he intended to curse, e.g. Yisrael should not have Batei Kenesiyos and Batei Midrash (Sanhedrin 105b). It was more than one word!