The place of the Temple on Mount Moriah is one of three places that the Tanakh tells us was purchased and paid for in full. In Sefer Shmuel (II Chapter 24) we are told of a plague that struck the Jewish people as a result of King David’s decision to count the people. Gad the Prophet instructs King David to build an altar on the place of the granary of Aravnah the Jebusite, the hilltop that was destined to become the place of the Temple. Aravnah offers his granary, together with his cattle for sacrifices and the morigim and other utensils as firewood, but King David insists on purchasing these from him.
The Gemara quotes a baraita that points out an apparent contradiction between the price paid by King David according to the story in Sefer Shmuel (II 24:24-25) and the parallel story as related in Sefer Divrei HaYamim, or Chronicles (I 21:25-26). While in Sefer Shmuel we learn that King David paid 50 silver shekalim, in Sefer Divrei HaYamim the price is reported as 600 gold shekalim. The baraita explains that David collected 50 shekel from each of the twelve tribes so that each would have a share in the 600 shekel price.
The Gemara relates that when Rava was learning this with his son they dealt with a further question – the difference between the silver shekalim in Sefer Shmuel and the gold shekalim in Sefer Divrei HaYamim. The explanation offered by Rava is that David collected silver shekalim from each tribe that added up to the value of 50 gold shekalim, so that the sum total collected was the value of 600 gold shekalim.
In a side comment, Ulla explains that the morigim that Aravnah wanted to donate were boards that were used to thresh the grain. In the time of the Mishnah these implements were still in use – as they still are today – albeit in a more developed form that allowed the animal driver to sit while the wheels of the morigim threshed the grain.