 the moons work and its place in the number. so you say 1 three ghurar. and ghurra/everything has its beginning. and a third of nafl 2. and a third of nine because its end is the ninth day. and a thirteenth because its beginning is the tenth. and a third of baid because it is white with the moon from its beginning to its end. and a third of a shield. and the analogy is a shield except that they followed 3 that which came before it and took it out from its place. and the singular is diraa.
عمل القمر وعلى محلها من العدد. فتقول ١ ثلاث غرر . وغره/ كل شىء اوله. وثلث نفل ٢ . وثلث تسع ، لأن آخرها اليوم التاسع. وثلث عشر لأن أولها العاشرة وثلث بيض لأنها تبيض بالقمراء من اولها إلى آخرها. وثلث درع . والقياس درع الا انهم أتبعوا ٣ ذلك ما قبله فأخرجوه مخرجه. والواحدة درعاء.