He—may Allah have mercy on him—was asked:

A man established an endowment and imposed conditions upon a group of Quran reciters: they were to attend every day after the dawn prayer and recite whatever they could of the Quran until sunrise, then take turns among themselves in pairs during the daytime, a day at a time. They were also to assemble after the afternoon prayer, each reciting two portions of the Quran, and to assemble every night preceding Friday. Their gatherings in this manner at his grave within the burial site total seventy-seven each month. He further stipulated that they spend every night at the aforementioned burial site, provided each of them with suitable accommodation, and assigned them regular stipends from the endowment’s proceeds, payable daily and monthly.

Are they obliged to attend as he stipulated? Or must they fulfil those requirements wherever they can perform their assigned recitation duties? Or is neither the place nor the time binding? Are they also obliged to spend the night at the aforementioned place, or not?

If these conditions are deemed binding, and one of them appoints someone to perform his assigned recitation duty under the endowment and at the specified place, while the founder stipulated in the endowment deed that they may appoint substitutes in cases of necessity, what constitutes the necessity that permits such substitution?