It is narrated from Sayyiduna Anas (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Whoever forgets to pray a prayer, let him pray it whenever he remembers it, and its expiation is only that he makes up the prayer." Then Qatadah recited this noble verse: "And establish prayer for My remembrance" [Surah Ta-Ha: 14].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3179