Idgham Mutajanisayn

Mutajanisayn, as mentioned earlier, means the two letters share the same articulation point but differ in quality. This occurs in:

— The Dental Letters (Nat'iyyah): Taa into Ttaa, Ttaa into Taa, Taa into Daal, and Daal into Taa.

◆ The Gum Letters (Lathawiyyah): Thaa into Dhaal, Dhaal into Zhaa

◆ The Labial Letters (Shafawiyyah): Baa into Meem

Hafs made Idgham obligatory in every occurrence of homogeneous letters meeting in the Quran, except for two places where both Idgham and Idhar are permitted — though Idgham is the transmission we recite by, through Ash-Shatibiyyah.

Obligatory Idgham for Homogeneous Letters (Hafs)

1. Feminine marker Taa (silent) into Ttaa:

﴾وَدَّت طَّٖائِفَةً مِنْ أَهْلِ الْكِتَابِ لَوْ يُضِلُونَكُم﴿ (Aal-'Imran: 69) — complete Idgham as seen earlier.

﴾إِذْ هَمَّت طَّٖائِفَتَانِ مِنْكُمْ أَن تَفْشَلاَ﴿ (Aal-'Imran: 122)

2. Silent Ttaa into Taa:

﴾لَئِن بَسَطتَ إِلَيَّ يَدَكَ لِتَقْتُلَنِي﴿ (Al-Ma'idah: 28) — incomplete Idgham, as the Ttaa disappears but its heaviness (isti'la and itbaq) remains.

﴾وَمِن قَبْلُ مَا فَرَّطتُمْ فِي يُوسُف﴿ (Yusuf: 80)

﴾فَقَالَ أَحَطتُ بِمَا لَمْ تُحِطْ بِهِ﴿ (An-Naml: 22)

3. Feminine marker Taa (silent) into Daal:

﴾فَلَمَّا أَثْقَلَت دَّعَوَا اللَّهَ رَبَّهُمَا﴿ (Al-A'raf: 189) — complete Idgham.

﴾ قَالَ قَدْ أُجِيبَت دَّعْوَتُكُمَا﴿ (Yunus: 89)

4. Silent Daal into Taa:

﴾قَد تِّبَيَّنَ الرُّشْدُ مِنَ الْغَيِّ﴿ (Al-Baqarah: 256)

﴾وَلَٴكِن يُ٘اخِذُكُم بِمَا عَقَّدتُّمُ الأَيْمَانَ﴿ (Al-Ma'idah: 89)

5. Silent Dhaal into Zhaa (occurs in two places):

﴾وَلَوْ أَنَّهُمْ إِذ ظَّلَمُواْ أَنُفُسَهُمْ ﴿ (Az-Zukhruf: 39)

﴾ وَلَن يَنْفَعَكُمُ الْيَوْمَ إِذ ظَّلَمْتُمْ أَنَّكُمْ فِي الْعَذَابِ مُشْتَرِكُونَ﴿ (An-Nisa': 64)

Permissible Idgham for Homogeneous Letters (Hafs)

6. Thaa into Dhaal: ﴾يَلْهَث ذَّلِكَ﴿ (Al-A'raf: 176)

7. Baa into Meem: ﴾يَا بُنَيَّ ارْكَب مَّعَنَا﴿ (Hud: 42)

In these two places, Hafs allows either Idgham or Idhar. Idgham is the transmission through Ash-Shatibiyyah, which we recite by.