Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) reports that the Prophet (peace and blessings be upon him) said: "Repentance from a sin is that when a man repents from it, he does not then commit that sin again."
Ahmad recorded it, and its chain is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب التوبة / 17524
Hadith Gradingمحدثین:إسنادہ ضعیف
Hadith Takhrij«اخرجه احمد فى المسند (4264) ، أخرجه مسند أحمد برقم: 4252»