To whom was the verse beginning with: "The life of this world is but play and amusement..." addressed, and what is its continuation and the Sura in which it was revealed?

This is part of a verse repeated in two places: in Surat Muhammad, verse (36), in its entirety: "This worldly life is only amusement and diversion. And if you believe and fear Allah, He will give you your rewards and will not ask you for your properties," and in Surat Al-Hadid, verse (20), in its entirety: "Know that the life of this world is only play and amusement, a show and boasting among yourselves, and a rivalry in respect of wealth and children. It is like the rain whose vegetation delights the disbelievers. Then it dries up and you see it turning yellow; then it becomes scattered pieces. And in the Hereafter there is a severe punishment, and forgiveness from Allah and [His] pleasure. And what is the worldly life except the enjoyment of delusion." The discourse in both is addressed to the believers. Al-Sa'di interpreted the verse from Al-Hadid by stating that Allah informs us about the reality of this world, that it is play and amusement, whereby bodies play and hearts are amused. This is the state of the people of the world who are heedless of the remembrance of their Lord, in contrast to the vigilant ones whose hearts are filled with the remembrance of Allah and who work for the Hereafter.