MB 23: According to the Raavad he must interrupt.. - The consensus among almost all the later authorities is that in the case of a biblical commandment we make a major distinction based upon whether he started [doing something else] with or without permission [i.e. before or after the time to do the commandment arrived]. Therefore according to this, if he was working or doing any of the other things mentioned here besides for eating, if he started before daybreak [the beginning of morning, over an hour before dawn] he need not interrupt what he's doing if there will be enough time after he's done to read Shema and to pray, because we rule later in Siman 89:7 that our Sages did not decree that one refrain from activity before the time for morning prayers. Therefore, he started his activity with permission. However, if he started after daybreak, which was without permission, he must interrupt to read Shema, but not for the blessings on Shema or for the Amidah. Afterwards, when he completes his work, he will be required to read Shema again with its blessings and to say the Amidah. This is only if there will be time left after he completes his work, but if he sees that the time is passing, he must interrupt immediately. In any instance where he need not interrupt what he is doing, he is not forced to stop even if he will miss praying with a congregation as a result. Concerning eating, it is apparent from the Shulchan Aruch in Siman 89:5 that he rules that one must stop eating immediately after daybreak even if he started with permission, and there is no way around it so long as has not prayed.
MB 24: And he reads - This wording implies that after he reads Shema, he may complete all these activities should he have started them even if he has not yet prayed, as we wrote in the previous MB; and this terminology is not literal concerning an instance where he was busy eating, because in a case of eating we already explained that he also has to pray first. This wording was used because he was mentioning the other activities. Or perhaps he mentioned it because of the evening reading of Shema, because there too all these laws are pertinent, and in the evening certainly if he started any of these five activities within a half hour before nightfall he must interrupt them immediately. Then when night falls he should read Shema without its blessings and afterwards finish eating or any other activity, and then read Shema with its blessings and pray the Amidah, as we see later in Siman 235:2. Look in the Pri Megadim there.
MB 25: Time to read - It is a decree lest the activity drag out and the time of the reading of Shema elapse. It is not comparable to the Mincha prayer where we rule in Siman 232 that if he started any of these activities before praying, he need not interrupt them, because since the reading of Shema is required by the Torah the Sages were more stringent about it.
MB 26: Siman 235 - He means to say that over there the difference between starting with permission and starting without permission is explained. See there for more information.
--Shmuel-Weidberg--shmuel@io.org--Toronto-Canada--