Sayyiduna Abdullah bin Umar (may Allah be pleased with them) narrated that the Messenger of Allah (peace and blessings be upon him) used to observe i'tikaf during the last ten days of Ramadan.

The purified wife of the Prophet (peace be upon him), Lady Aisha (may Allah be pleased with her), narrated that the Prophet (peace be upon him) continuously observed i'tikaf in the last ten days of Ramadan until his death, and after him, his purified wives continued to observe i'tikaf.

Lady Aisha (may Allah be pleased with her) narrated that the Prophet Muhammad (peace and blessings be upon him) used to observe i'tikaf in the last ten days of Ramadan. I would set up a tent for him (in the mosque), and after performing the morning prayer, he would enter it. Then Lady Hafsa sought permission to set up a tent (for her i'tikaf), and Lady Aisha granted her permission, so she set up a tent. When Lady Zainab bint Jahsh saw this, she also set up a tent (for herself). In the morning, when the Messenger of Allah (peace and blessings be upon him) saw several tents, he asked, "What is this?" He was informed of the reality of the matter. He said, "Do you think these tents have been set up with the intention of earning reward?" So he abandoned i'tikaf for that month (of Ramadan) and observed i'tikaf for ten days in Shawwal.

Narrated by Sayyidah Aisha (may Allah be pleased with her): When the last ten days (of Ramadan) would begin, the Prophet Muhammad (peace be upon him) would tighten his waist-wrapper (i.e., he would prepare himself with full determination), and he would stay awake during the nights and also wake up his family members.