Hariri was in Saudi Arabia for two weeks, leading to speculation he wasn't allowed to leave.
Hariri has been in Riyadh since his resigned as Lebanon's prime minister, leading some to suspect Saudi Arabia called on him to step down.
Almost a week after his surprise resignation, Lebanon's former prime minister still hasn't returned from Saudi Arabia.
The anti-corruption campaign kicked off Saturday when 11 other princes, four ministers and a number of former ministers were arrested.
The two prominent Islamic countries are locked in a Cold War-like struggle for regional dominance.
Many saw the move as a way to concentrate power under the king's son and successor.
Saad al-Hariri claims Iran and Hezbollah are interfering with Arab world affairs.
The kingdom's General Sports Authority said Sunday that stadiums in Jeddah, Dammam and Riyadh are preparing to "accommodate families" in early 2018.
Sophia is a robot that also happens to be one the newest citizens of Saudi Arabia. The unprecedented move has left some human rights activists upset.
The defense system is meant to protect them from neighbors like Iran.
The country's king issued a decree allowing women to apply for driver's licenses.
Muslims from around the world will converge in Mecca, Saudi Arabia, for one of the largest religious gatherings in the world.