Hizb 21 opens Juz 11, closing At-Tawba entirely within its first quarter before crossing into Yunus for the remainder, another instance in this account of a hizb spanning two suras with no additional mark distinguishing the seam beyond the ordinary chapter heading. In tarawih recitation this hizb typically opens the eleventh night, and the closing verses of At-Tawba carried here, describing the Prophet's own grief and mercy for his community, are frequently recited with particular tenderness regardless of where the hizb boundary itself happens to fall.
Because At-Tawba's final verses and Yunus's opening argument both address the theme of doubt, doubt about whether ordinary companions could truly be forgiven, doubt about whether an ordinary man could truly be a prophet, this hizb is sometimes used by teachers to show how the thirty-juz scheme can, by coincidence rather than design, place two suras that share a concern for doubt and reassurance directly on either side of the same boundary.
Huffaz reviewing this hizb by quarter typically treat the three companions' story as the section's clearest anchor, a compact narrative with named individuals inside a stretch otherwise given over to more general argument.