Sayyiduna Awf bin Malik al-Ashja'i (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever reads one letter of the Qur'an, one good deed is written for him." I do not say that "Alif Lam Mim, Dhalika al-Kitab" (is one letter); rather, Alif is a separate letter, Lam is a separate letter, Mim is a separate letter, Dhal is a separate letter, and Kaf is a separate letter.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15232