Shu'aib bin Abi Hamza شعيب بن أبي حمزة · The Book of the Masjids

"The Messenger of Allah (ﷺ) entered the House (the Ka'bah), with Usamah bin Zaid, Bilal and 'Uthman bin Talhah, and they locked the door behind them. When the Messenger of Allah (ﷺ) opened it, I was the first one to enter. I met Bilal and asked him: 'Did the Messenger of Allah (ﷺ) pray inside?' He said: 'Yes, he prayed between the two Yemeni columns.'"

"When any one of you enters the Masjid, let him pray two Rak'ahs before he sits down."