Jamieson, Fausset and Brown on Daniel 11:33

33. they that understand--who know and keep the truth of God (Is 11:2).

instruct many--in their duty to God and the law, not to apostatize.

yet they shall fall--as Eleazar (2 Maccabees 6:18, &c.). They shall be sorely persecuted, even to death (He 11:35, 36, 37; 2 Maccabees 6, 7). Their enemies took advantage of the Sabbath to slay them on the day when they would not fight. Tregelles thinks, from comparison with Da 11:35, it is the people who "fall," not those of understanding. But Da 11:35 makes the latter "fall," not an unmeaning repetition; in Da 11:33 they fall (die) by persecution; in Da 11:35 they fall (spiritually) for a time by their own weakness.

flame--in caves, whither they had retired to keep the Sabbath. Antiochus caused some to be roasted alive (2 Maccabees 7:3-5).

many days--rather, "certain days," as in Da 8:27. Josephus [Antiquities, 12:7.6,7] tells us the persecution lasted for three years (1 Maccabees 1:59; 4:54; 2 Maccabees 10:1-7).