"The Messenger of Allah would Yujawir (stay in I'tikaf) during the last ten (nights) of Ramadan and he said: 'Seek the Night of Al-Qadr during the last ten (nights) of Ramadan.'"
Jami` at-Tirmidhi Book 8, Hadith 111
← Previous Hadith "When the Messenger of Allah wanted to perform I'tikaf, he would perform Fajr prayer and then he would enter his place of I'tikaf."

Jami` at-Tirmidhi Book 8, Hadith 110 Next Hadith → "I said to Ubayy bin Ka'b: 'O Abu Al-Mundhir! How do you know that it is the night of the twenty-seventh?' He said: 'Rather, the Messenger of Allah informed us that it is a night (after which) the sun rises without rays, so we counted and we remembered it. By Allah! Ibn Mas'ud learned that it is in Ramadan and that it is the nigh of the twenty-seventh, but he did not want to inform you lest you would depend on it."

Jami` at-Tirmidhi Book 8, Hadith 112