Ibn al Qayyim rahimahullah:
“For the people of sins there are three great rivers with which they purify themselves in this world and if these do not suffice in purifying them, then they are purified in the river of Hell-fire on the Day of Judgment:
1. A river of sincere repentance
2. A river of good deeds that drowns the sins that surround it.
3. And a river of great calamities (that befall the sinner) that expiate (his sins)
Therefore, when Allah intends good for His slave, He enters him into one of these three rivers, so he comes purified and cleansed on the Day of Judgement, not requiring the fourth purification.