Abu Sa ‘id al-Khudri (Radi Allah Anhu) reported that Allah’s Messenger (sal-allahu- alleihi-wasallam ) spent in devotion (in i’tikaf) the middle ten nights of the month of Ramadan, and when twenty nights were over and it was the twenty-first night, he went back to his residence and those who were along with him also returned (to their respective residences). He spent one month in devotion. Then he addressed the people on the night he came back (to his residence) and commanded them as Allah desired (him to command) and then said: I used to devote myself (observe i’tikaf) during these ten (nights). Then I started devoting myself in the last ten (nights). And he who desires to observe i’tikaf along with me should spend the night) at his place of i’tikaf. And I saw this night (Lailat-ul-Qadr) but I forgot it (the exact night) ; so seek it;In the last ten nights on odd numbers.
[Sahih Muslim : Book 6, Book Name 'Kitab Al-Sawm' Number 2625]
