when one is saying tehillim with a group, to complete the sefer daily, and is negligent in saying their perakim, can this be compensated for? can it be done by others? may i request the source for this answer? thank you.
Shalom, Your question is one concerning fulfilling one's vows. A group, or individual, who promises to do something, especially a mitzvah like reciting Tehillim, is obligated to stick to their word. This is a Torah obligation, to which the Torah refers many times -see Bamidbar 30,3, and Devarim 23, 22-24. Because of the severity of this law, I am sure that before you took upon yourself to say Tehillim daily, you made a verbal statement to the effect that it would not be a binding oath, such as saying "B'li Neder" ("this is not to be considered as an oath"). See the Kitzur Shulchan Aruch chapter 67 for more imformation on this subject. That being the case, i.e. that you did not make an oath or vow, but rather said it was not binding, you are not technically obligated from the point of view of vow taking. (If it was a vow, or you did not say "Bli Neder" see below). However as you are saying the Tehillim for the benefit of someone, that spiritual merit you desired to create will be lacking. As such you should certainly "make-up" the tehillim as soon as possible. If possible by the person who undertook the task in the first place, but even someone else may help in this. I would like to point out that I have no source for this. I say this not (only) for the purpose of being honest, but also to stress an important point that I feel needs to be made. The practice of groups or individuals saying Tehillim, or other prayers and learning, for the merit of others is to be praised. It is certainly a widespread and wonderful thing. However, it is not an obligation, nor does it have "halachot" surrounding it. Just as someone who took upon themselves, "bli neder", to call up their lonely friend daily, we would say it is a great thing. But if they missed a day they would not be asking their Rabbi "can I make it up by calling twice tomorrow?" So too here - saying the Tehillim is praiseworthy, but not a halachically defined practice in the way the daily prayer service is, or saying after blessings on food are. In those cases we can ask what we are obligated to do when we missed the mitzvah - but this is not the case with Tehillim groups. There is a discussion in halacha concerning fulfilling one's daily learning quota, and whether and how it can be made up for in the event of missed days (see Shulchan Aruch Orach Haim 155,1 mishna brura 4, and 238,1 and the mishna brura there). However the discussion there concerns the question of fulfilling one's vows, and as we wrote above, advises one to always say "Bli Neder" before taking on an obligation, or set daily learning (see mishna brura there), and this would certainly be true in the case of saying Tehillim daily. If one did not say "Bli Neder" or the like - it could be that there is a problem of fulfilling one's oaths. However, as the "taking on" of saying the Tehillim was likely done just through the act of saying the Tehillim daily, and not through a verbal oath, such as "I promise to say Tehillim every day", the law is more lenient. This being the case, one should follow what I wrote above - but in the future one should be very careful to say "Bli Neder" before taking on saying daily Tehillim or other meritorious acts. Blessings.