Special Mudhafs:فَوقَ،تَحْتَ ،قَبْلُ ، بَعْدُ

The words :فَوقَ،تَحْتَ ،قَبْلُ ، بَعْدُ are special mudhafs.

If the mudhaf ilaih is present then they are fully flexible like we see in

مِنْ قَبْلِكُمْ and مِنْ قَبْلِهِ

But many a times the mudhaf ilaih is omitted – then they become non flexible-
they are just fixed to their original harakah then – like dhamma with قَبْلُ and fathah with تَحْتَ

So we see it as:

مِنْ قَبْلُ

as the mudhaf ilaihi is omitted.

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