In the name of Allah The Compassionate The Loving.
RULES for م Sakinah
Salam alaikum wa rahmatu Allahi wa BarakatuHu. Peace be upon the followers of guidance.

meem rules

The م sakinah, which does not have a haraqah (vowel) on it, falls into one of three categories, depending on what letter comes after it.

First: AL- Ikhfaa Shafawee الإخفاء, when the letter following the م sakinah is a ب .

The ب is a lip letter just like the م. When the ب follows the م sakinah, the م sakinah is pronounced with Ikhfaa Shafawee الإخفاء . The م sakinah begins to be pronounced from the lips and then leaves in a clear pronounciation when reaching the ب. The complete ghunnah (nasalization) is repressed, thus producing the Ikhfaa Shafawee الإخفاء sound. Some of the ulema of say it is pronounced as if there was a date between the lips. The length of the sound is also extended.

as in:

{يَعْتَصِم بِاللَّهِ}

{يَوْمَ هُم بَارِزُونَ}

The م sakinah is also pronounced with Ikhfaa Shafawee الإخفاء, when you have the iqlaab of the ن sakinah and tanween; i.e. when the ن changes to a م , because the inherent characteristics are the same.

Second: AL-Idgham Mithlain Sageer إدغام مثلين صغيرا, when the letter following the م sakinah is another م .

It is required to pronounce the م sakinah in this case with lenghthened ghunnah (nasalization).
as in:

{خَلَقَ لَكُم مَا فِي الأَرْضِ}

It is also pronounced this way whenever the م has a shaddah above it ( مّ ) .

It is a good idea to pronounce along with your shaikh in order to practice the correct length. Allah willing you will be continuing on the chain of our pious predecessor ulema.

Third: Clear , AL- Idhhar shafawi إظهارًا شفويًا, when any of the rest of the letters follow the م sakinah.
It is required to pronounce the م sakinah in this case clearly and concisely (quickly) without the ghunnah (nasalization) that is present in the rest of the letter. This is whenever any of the 26 remaining letters follow the م sakinah, including the ف and the و which are also lip letters.
as in:


{لَعَلَّكُمْ تَتَّقُونَ}


Repeat after the following ayats, and state the rule for the م sakinah:

{لَكُمۡ دِينُكُمۡ وَلِىَ دِينِ}

{عَمَّ يَتَسَآءَلُونَ}

{ٱلۡحَمۡدُ لِلَّهِ رَبِّ ٱلۡعَـٰلَمِينَ}

{فَأَمَّا مَنۡ أَعۡطَىٰ وَٱتَّقَىٰ}

{وَلَمۡ يَكُن لَّهُ ۥ ڪُفُوًا أَحَدٌ}

{أَوۡ كَصَيِّبٍ۬ مِّنَ ٱلسَّمَآءِ فِيهِ ظُلُمَـٰتٌ۬ وَرَعۡدٌ۬ وَبَرۡقٌ۬}

{وَٱلشَّمۡسِ وَضُحَٮٰهَا}

{ٱللَّهُ ٱلَّذِى خَلَقَكُم مِّن ضَعۡفٍ۬ ثُمَّ جَعَلَ مِنۢ بَعۡدِ ضَعۡفٍ۬ قُوَّةً۬ ثُمَّ جَعَلَ مِنۢ بَعۡدِ قُوَّةٍ۬ ضَعۡفً۬ا وَشَيۡبَةً۬‌ۚ }

{يَعْتَصِم بِاللَّهِ}

{يَوْمَ هُم بَارِزُونَ}