There are three rules regarding the Meem Saakin
1. Ikhfa Shafawi
2. Idghaam Shafawi
3. Ithaar Shafawi
These will now be explained below
1. Ikhfa Shafawi – Meem Saakin
When the letter Ba (ب) appears after a Meem Saakin (مْ) there will be Ikhfa Shafawi. It will be pronounced with a light nasal sound in the nose for a duration of 2 harakah (2-3 second duration).
Example:
2. Idghaam Shafawi – Meem Saakin
If after a Meem Saakin (مْ) there appears a Meem Mushaddah (مّ), Idghaam will occur. In other words, the two Meems will become incorporated and be read with Ghunna (nasalization).
Example:
3. Ithaar Shafawi – Meem Saakin
When after a Meem Saakin (مْ) there appears any of the 26 letters other than the letters Ba and Meem, there will be Ithaar Shafawi. No Ghunna will occur.
Example: