al-ʿĀdiyāt— The Courser

It carries an instance of al-Sūsī's major assimilation (idghām kabīr). The first couplet lists the ten letters into which the dāl assimilates — the initials of كِلْمٌ تُرْبُ سَهْلٍ ذَكَا شَذًا ضَفَا ثُمَّ زُهْدٌ صِدْقُهُ ظَاهِرٌ جَلَا; the second says the tāʾ assimilates into those same ten and into the ṭāʾ besides, with two transmitted wajhs for him in a handful of words.

Both were read with assimilation. Its justification: the tāʾ merges into these letters because they share its region — the tongue-tip and the roots of the incisors. As for merging tāʾ into ḍād, the ḍād is articulated from the middle of the tongue rather than its tip, but it possesses a spreading (tafashshī) by which its sound reaches the tongue-tip and incisor roots, so it too becomes a neighbour of the tāʾ, as the dhāl, sīn, ṣād and zāy neighbour it; hence merging it is admissible. The rest read all these letters with iẓhār, on the ground that the points of articulation differ and the letter receiving the tāʾ is not obligatorily adjacent: notice that in اقْتَتَلُوا the tāʾ is not merged into the tāʾ, since that pattern does not oblige it — it is the tāʾ of iftaʿala — and if it stays unmerged inside a single word, across two words all the more. (al-Mūḍiḥ 3:1083)

An idghām kabīr of al-Sūsī's, and Khallād agrees with him here, with khulf transmitted from him; but Khallād is not allowed tawassuṭ or qaṣr of the alif before the doubled letter — for him the saturated madd is obligatory — unlike al-Sūsī, for whom all three lengths are admissible.