¡ Alif. Lām. Mīm.
1 Alif, lām, and mīm are the same letters that start the previous sūrah. See 2:1c. They could represent “God knows best” (Allāhu aʿlam); or Allāh, Jibrīl, and Muḥammad; or the alif of oneness (i.e., as the first letter), the lām of kindness (luṭf), and the mīm of sovereignty (mulk; Su).