Tafsir of Qaf 50:5

{Nay, they denied the truth} This is a second disjunctive particle (idrab) following the first, indicating that they have committed something even more heinous than their astonishment: the denial of the Truth—which is the Prophethood established by miracles—at the very first instance, without reflection or contemplation.

{So they are in a confused state} Meaning: in a state of disorder. It is said: "The ring became loose (maraja) on his finger," meaning it shifted. They say at one time: "He is a poet," at another: "A sorcerer," and at another: "A soothsayer." They do not remain steadfast on any single thing.

It is also recited as: (Lamma ja'ahum) with a kasra on the lam, where ma is the infinitive particle (masdariyyah). The lam here is the same as in the expression "five days have passed" (li-khamsin khalaw), meaning: "at the time of its coming to them."

It is said: {The Truth} refers to the Quran. It is also said: It refers to the news of the Resurrection.