That is from the news of the unseen which We reveal to you, [O Muḥammad]. And you were not with them when they cast their pens1 as to which of them should be responsible for Mary. Nor were you with them when they disputed.
The story of Zachariah and Mary is one of the reports of [the Ghaib] which I reveal to you, O Messenger. You were not there with those scholars and worshippers when they argued about who was most entitled to raise Mary. They eventually decided to draw lots by throwing their pens, and the pen of Zachariah (peace be upon him) won.