Sayyiduna Zayd bin Thabit (may Allah be pleased with him) used to spend the twenty-third and twenty-seventh nights of Ramadan in worship, but not with the same devotion with which he worshipped on the seventeenth night. He was asked: Why do you single out the seventeenth night? He said: "On this night the Qur'an was revealed, and on its morning a distinction was made between truth and falsehood, and on the morning of this night he would rise with a face shining with joy."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4846