What is the rule for vocalizing the soft waw when it meets a silent letter in another word: is it by ḍammah as in (دعوُ الله – they called upon Allah) or by kasrah as in (لوِ استطعنا – if we were able)? And what is the meaning of al-iḍmār (implication/concealment) and al-ziyādah (addition/redundancy) that Imam Abu Amr al-Dani mentioned in his book al-Taḥdīd, in likening the hāʾ of a demonstrative pronoun to the hāʾ of a possessive pronoun?

The soft, quiescent waw at the end of a word, if followed by a quiescent letter at the beginning of the next word, is moved with a kasra (vowelization with 'i') to avoid the meeting of two quiescent letters, as in: {وَأَلَّوِ اسْتَقَامُوا} (And if they had remained on the straight path). If the quiescent letter is "dead" (a long vowel/madd), it is dropped in continuous recitation (wasl) and maintained in a pause (waqf), as in: "قالوا اللهم" (They said: O Allah). The rule is that if two quiescent letters meet, the first is given a kasra if it is "alive," and it is dropped in continuous recitation if it is "soft" (dead). As for "دعوا الله" (They invoked Allah), its origin is "دعووا," and one of the two waws was dropped. The remaining waw was moved with a dhamma (vowelization with 'u') instead of a kasra to indicate the dropped waw.

As for the letter ha' in the demonstrative pronoun "هذه" (this - feminine), it resembles the pronominal ha' in the rule of lengthening (silah) and shortening (qasr). So, it is lengthened with a ya' before a vowelized letter, and its lengthening is dropped before a quiescent letter, as in the Almighty's saying: {وَهَذِهِ الْأَنْهَارُ} (And these are the rivers). The pronominal ha' is the extra ha' that indicates a singular masculine, and it is lengthened with a waw if it has a dhamma and with a ya' if it has a kasra. The opposite of lengthening is shortening (i.e., not lengthening).