Fiqh, evidence & legal reasoning: Placing beams on a neighbor’s wall

One of my current book projects is something that will give students of fiqh a taste of the evidence behind rulings and legal reasoning, as well as a few hints as to why one opinion is preferred over others. Here’s an example from the section on reconciliation within the chapter on trade.

One cannot be forced to allow beams to be placed upon walls that are shared or privately owned.

It is permissible to take something in exchange for letting water flow, the right to build or place beams. This is because it involves exchanging things that are permissible and intended. And one does not have to agree to the above for free, since he ﷺ said, “A Muslim’s property is not licit except what he gives willingly.”1

In the old school [i.e., Imām al-Shāfiʿī’s positions before going to Egypt], al-Shāfiʿī considered it obligatory due to him ﷺ saying, “No neighbor is to prevent his neighbor from placing [a beam of] wood on his wall.”2 In the new school, Imām al-Shāfiʿī interpreted it to be recommended due to the first hadith. According to the old school, there were conditions for it being obligatory…

  1. Aḥmed (23605), al-Dāraquṭnī (19645 [3:26 #92]), al-Bayhaqī (11325) and in Maʿrifat al-Sunan (11979). 
  2. Al-Bukhari (2463), Muslim (1609 #136), Abū Dāwūd (3629), al-Tirmidhī (1353), Ibn Mājah (2335).