Sayyidina Abu Dharr narrated : We kept fast with Allah’s Messenger. He did not pray with us till seven (nights) remained in the month when he stood with us (in prayer) till the third of the night passed away. Then he did not stand with us on the sixth (last ningh) but stood with us (in salah) on the fifth (last night) till the middle of the night was gone. So, we submitted, “0 Messenger of Allah! Would that you had prayed the supererogatory (salah) with us for the remainder of the night. “He said, “He who stood with the Imam till he finishes has a full night’s standing (in salah) recorded for him”. Thereafter, he did not pray with us till three (nights) remained in the month, He prayed (the salah) with us on the third (last night) and called the folk of his house and his wives, standing so long that we feared that we might miss al-falah.
The sub-narrator said that he asked him, “What is al-falah?” He said, “It is sahr (predawn meal)”.
[Ab 21476, Abu Dawud 1375, Nisai 1364, Ibn e Majah 1327]