Translation:

28. And know ye that your possessions and your progeny are but a trial; and that it is Allah with whom lies your highest reward.

Notes (Tafseer)

1201. A big family-many sons-was considered a source of power and strength: iii. 10, 116. So in English, a man with many children is said to have his "quiver full": Cf. Psalms, cxxvii. 4-5: "As arrows are in the hands of a mighty man, so are the children of thy youth. Happy is the man that hath his quiver full of them; they shall not be ashamed, but they shall speak with the enemies in the gate." So with property and possessions: they add to a man's dignity, power, and influence. But both possessions and a large family are a temptation and a trial. They may turn out to be a source of spiritual downfall, if they are mishandled, or if the love of them excludes the love of Allah.