وَرَأَيْتَ النَّاسَ
And you see the people. (110:2)
Raʾayta is a past verb with a second-person subject suffix, and al-nās is its object. Within the frame set by idhā, wa-raʾayta adds a further event or circumstance. The direct viewpoint of seeing people makes the statement more than an abstract report of numerical change: it creates a visible communal scene.
Verbs of seeing may have different constructions when used for physical perception or cognition. Here the depiction of people entering is naturally understood as observation.