Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates this statement of the Prophet (peace and blessings of Allah be upon him): "Is any one of you incapable of reciting one third of the Qur'an every night?" We said: "O Messenger of Allah (peace and blessings of Allah be upon him), who among us can do that?" The Prophet (peace and blessings of Allah be upon him) said: "Reciting Surah Ikhlas is equal to reciting one third of the Qur'an."
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2576
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «الروض النضير» (1024).فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناد صحيح على شرط الشيخين