The Quran was revealed piecemeal (25:32) during a period of 23
years (609-632 C.E.), the shorter chapters generally, and some of
the larger ones, being revealed entire and at one time, while the
revelation of the majority of the larger chapters and some of the
shorter chapters extended over many years. The practice was that
when a chapter was revealed in parts, the Holy Prophet specified,
under Divine guidance, the place of the verse revealed, and thus
the arrangement of verses in each chapter was entirely his work.
Similarly, later on when a considerable portion had been
revealed, the arrangement of the chapters was also the work of the
Holy Prophet himself.