Why is the article lām clear in «الْمِسْكِينِ»?

Al-Māʿūn and Al-Humazah: Applied Assimilation, Concealment, Madd and Hāʾ Rules

• Nūn sākinah meets bāʾ
• It involves major ṣilah
• It is followed by mīm, a moon letter
• Mīm is a sun letter