Derivatives of the root w-ṣ-l are used in Arabic grammatical theory to express the general idea of ‘connecting’ two linguistic units. Two terms derived from this root, waṣl and ṣila, are used as technical terms, along with mawṣūl as the correlate of ṣila, and the verbs waṣala, ʾawṣala, and ittaṣala.

The use of ṣila as a technical term goes back to the earliest Qurʾānic commentaries. Here, the term is used for redundant elements whose only function is to come between two linguistic units. Examples are found in Muḥammad al-Kalbī's (d. 146/763) commentary, for instance when he uses the term ṣila…