«وَكَالنَّفْسِ الْوَاحِدَةِ»
And like a single soul.
The comb simile highlights visible equality; the image of one soul goes further, suggesting inner unity of purpose and sentiment. The companions are presented as more than travellers sharing a road.
Al-nafs is grammatically feminine, and al-wāḥidah agrees with it as a feminine adjective. Grammar and literary interpretation reinforce one another in a compact phrase.
«فِي التِئَامِ الْأَهْوَاءِ»
That is, their inclinations were closely joined.
Iltiʾām means joining together, specifying the intended meaning of the one-soul simile.