Tafsir of Al-Inshiqaq 84:24

This [pronoun of] consequence (fa) is connected to the report of His Almighty’s knowledge of what they conceal, intending by this their retribution for their denial. It is also said that the fa is fasiha (eloquent), meaning: "If their state is as has been mentioned, then give them tidings, etc."

"Glad tidings" (tabshir) is, in common usage, informing one of something that brings joy. Its use here is by way of sarcasm, similar to the greeting of a painful blow.

It has been permitted that this is [used] because their immersion in sins—which necessitate punishment—and their failure to refrain from them, places them in the position of those who desire the punishment, until the report of it becomes like glad tidings or news of something pleasing. The difference between these two perspectives is apparent upon the slightest reflection.

It is extremely far-fetched for one to say that this is an allusion to the love of the Prophet of Mercy—may Allah Almighty grant him peace—for glad tidings; therefore, the term "glad tidings" is metaphorically applied to the command given to him—upon him be blessings and peace—to warn, as a way to soothe his heart—may Allah Almighty grant him peace.