Madd — Elongation Rules
Madd Lazim المَدّ اللَّازِم
A madd letter followed by a permanent sukoon — held for the full six counts.
When a long vowel is followed by a sukoon that is permanent (not from stopping), the elongation is lazim — necessary, and held for six counts without variation. It is the longest madd in the science. Lazim has four sub-types (kalimi muthaqqal/mukhaffaf and harfi muthaqqal/mukhaffaf), differentiated by whether the sukoon falls on a letter or follows a shadda, and whether it occurs in a word or in one of the disjointed letters (huroof muqatta'at).
Quran examples
الٓمٓ
The huroof muqatta'at at the start of Al-Baqarah — each letter's madd is held 6 counts. · 2:1
وَلَا ٱلضَّآلِّينَ
The alif before the shadda in ad-daallin is held 6 counts. · 1:7