It is narrated from Sayyiduna Wathilah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "The scrolls of Ibrahim (peace be upon him) were revealed on the first night of Ramadan; the Torah was revealed on the 6th of Ramadan; the Injil was revealed on the 13th of Ramadan; the Zabur was revealed on the 18th of Ramadan; and the Qur'an was revealed on the 14th of Ramadan."
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18405