The Study Quran's commentary collects the hadith tradition behind a claim already noted on this passage, that reciting al-Ikhlas equals reciting a third of the Quran, and explains why classical commentators thought the comparison made sense rather than treating it as pious exaggeration. The Quran's content is traditionally divided into three broad subjects, doctrine concerning God, law governing conduct, and accounts of past nations and the hereafter; al-Ikhlas, commentators argue, states the first of the three in full and states nothing else, so a reciter who says it has covered, in miniature, one whole third of what the entire text addresses.
The commentary tradition treats the sura's four lines as the most concentrated statement of tawhid, the oneness of God, anywhere in the Quran, denser even than the Throne Verse because it carries no supporting description, only the bare assertion and its three explicit denials, no partner, no offspring, no equal. That density is also why the sura functions in ordinary devotional life as a short recitation for protection and for the dead, said at burials and taught to children before longer suras, precisely because its shortness lets it carry the whole of Islamic theology proper in a form simple enough to memorize first.