To what extent is the hadith "Repentance nullifies what came before it" authentic, and is it a hadith in the first place?

The phrase "Repentance expiates what preceded it" has no known origin as a prophetic hadith. However, its meaning is sound and resembles the hadith in Sahih Muslim: "Do you not know that Islam demolishes what came before it? And that migration (Hijrah) demolishes what came before it? And that Hajj demolishes what came before it?"