Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) observed i'tikaf in the last ten days, and a hut (i.e. a small chamber) of palm leaves was built for him (peace and blessings be upon him). One night the Prophet (peace and blessings be upon him) put his head out of it and said: "O people! When the one praying is offering prayer, he is in intimate conversation with his Lord, so let him consider what he is saying to Him in that conversation. And do not raise your voices over one another!"
Ahmad, al-Bazzar and al-Tabarani in al-Mu'jam al-Kabir recorded it; its chain contains Muhammad bin Abi Layla, and there is criticism concerning him. I say: In the Sahih, only the mention of the i'tikaf from this hadith is found.