'Aishah (May Allah be pleased with her) reported:
The Prophet ﷺ used to engage himself in I'tikaf (seclusion for prayers) in the mosque during the last ten nights of Ramadan till he passed away; thereafter, his wives followed this practice after him.

[Al-Bukhari and Muslim].

وعن عائشة رضي الله عنها أن النبي ﷺ كان يعتكف العشر الأواخر من رمضان، حتى توفاه الله، تعالى ثم اعتكف أزواجه من بعده. ((متفق عليه))