Can Istighfar increase Rizq? What does the Qur’an actually say?

 Allah's Forgiveness Brings Blessings

Yes. Asking Allah for His forgiveness may even lead to an increase in one's lifespan, so why not an increase in provision as well? Allah Himself promises that seeking His forgiveness is a means for increasing wealth and children.

"And said, 'Ask forgiveness of your Lord. Indeed, He is ever a Perpetual Forgiver. He will send rain upon you in abundance, and give you increase in wealth and children, and provide for you gardens and rivers.'"

Surah Nuh (71:10–12)

The Prophet ﷺ also said:

"Nothing increases lifespan except righteousness, and nothing repels divine decree except supplication."
— Jamiʿ al-Tirmidhi 2139 (hasan)

All of these changes and alterations are already written in Al-Lawḥ al-Maḥfūẓ (the Preserved Tablet). Allah knew and decreed from eternity that a person would make duʿā', seek forgiveness, perform righteous deeds, and that, as a result, their provision, blessings, or lifespan would increase according to His decree. Nothing occurs outside Allah's perfect knowledge and decree.