Detailed Exegesis

Orphans (yatīmayn): Among humans, one who loses his father during childhood is called an “orphan” (yatīm), one who loses both parents is called a “double orphan” (laṭīm), and one who loses their mother is called motherless (ʿajī).(421)(420)

You could not (lam tastaṭiʿ): Capability (istiṭāʿa) means ability and is from the verbal form iftiʿāl. Sometimes its tāʾ is omitted for ease of pronunciation—since it is close in articulation to ṭāʾ—and it is said “isṭāʿa, yasṭīʿu.” In the verse under discussion, the jussive particle lam has also caused the omission of the yāʾ.(422)