وَمَنْ يَعْمَلْ مِثْقَالَ ذَرَّةٍ شَرًّا يَرَهُ
And whoever does an atom’s weight of evil will see it. (99:8)
وَإِنَّهُ عَلَىٰ ذَٰلِكَ لَشَهِيدٌ
And he is assuredly a witness to that. (100:7)
In the first passage, wāw joins parallel conditionals that together cover contrasting kinds of deeds. In the second, it joins a further assertion to the report of human ingratitude. The jāmiʿ differs: comprehensive moral contrast in one case and a related testimony in the other.
By comparison, an explanatory answer can stand without wāw while remaining strongly connected to the question implied by the context. Thus faṣl and waṣl are not reducible to the presence or absence of a particle alone; their justification rests in discourse relations.