When a reminder comes to them from their Lord that is new, they listen to it while playing.
Translation endnotes
[21:2-3] The Quran is the only miracle given to Muhammed (29:51). Muhammed's mushrik companions could not comprehend that a book could be a miracle, and they wanted miracles "similar" to the ones given to the previous prophets (11:12; 17:90-95; 25:7,8; 37:7-8). Modern mushriks also demonstrated a similar reaction when God unveiled the prophesied miracle in 1974. When the miracle demanded from them the dedication of the system to God alone, and the rejection of all other "holy" teachings they have associated with the Quran, they objected, "How can there be mathematics in the Quran; the Quran is not a book of mathematics" or, "How can there be such a miracle; no previous messenger came up with such a miracle!" When a monotheist who was selected to fulfill the prophecy and discover the code started inviting his people to give up polytheism and the worship of Muhammed and clerics, he was declared an apostate by Muslim scholars in 1989, and within a year he was assassinated by a group linked to al-Qaida in early 1990 in Tucson, Arizona. See 3:81; 40:28-38; 72:24-28; 74:1-56. For the prophetic use of the word reminder (ZKR), see 15:9; 21:2; 21:24,105; 26:5; 29:51; 38:1,8; 41:41; 44:13; 72:17; 74:31,49,54.