Sayyiduna Abdullah bin Qurt (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "Whoever offers a prayer and does not offer it completely, it (the obligatory prayer) will be supplemented from his voluntary prayers."
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1607