What does ʿan emphasize in ʿan ṣalātihim sāhūn?

Supplementary Practice 21: Comparative Rhetorical Study of Sūrat Quraysh and al-Māʿūn

• Neglect regarding the duty of prayer
• Treat ʿan and fī as interchangeable in every context
• Limit negligence to an occasional lapse inside prayer
• Treat the prepositional phrase as an adjective of hum