Why is the madd sound dropped at wa-aqīmū ṣ-ṣalāh?

Meeting of Two Sākin Letters — ʿAlā Ḥaddih, Ghayr Ḥaddih and Tanwīn

• Lām is always omitted
• Every ḍammah requires madd
• It is not Qurʾānic
• Two sākin elements meet in liaison