Cast as part of a domestic anti-corruption drive, the arrests also left Saudi Crown Prince Mohammed bin Salman in undisputed control of Saudi security services.
Riyadh subsequently accused Lebanon of declaring war on it because of Hezbollah.
Here is what we know. The comments were his first in public since he quit from Riyadh on November 4.
Saudi Arabia has stepped up its rhetoric against Hezbollah and its patron, Iran, accusing both of supporting Shiite rebels in Yemen known as Houthis.
The race turned into a political rally, with numerous runners calling for the return of Hariri, who has not publicly spoken since unexpectedly announcing his resignation.
His remarks came during a television interview with Lebanese journalist Paula Yacoubian in Riyadh, where Mr Hariri has remained since his resignation. But he is a strategically significant player in the relations between the two countries. Though Mr Hariri and Hizbollah had always been political rivals and at times bitter enemies, Mr Hariri managed to walk a fine line between appeasing both the group and the demands of Saudi Arabia, his own foreign patron. "Saudi Arabia is ready to pay tens of billions of dollars to Israel for that", he said.
"I am proud of the consensus we reached, and I am not turning my back on it and want it to succeed", Mr Hariri said on Sunday.
"He looked like a broken man who did not believe what he was saying, who is following orders and relaying a specific message", said Randa Slim, a fellow at the Middle East Institute in Washington.
Lebanon President Michel Aoun said before the interview that the "mysterious circumstances for Hariri's stay in the Saudi capital of Riyadh makes all his positions questionable and in doubt and not of his own volition".
US Secretary of State Rex Tillerson on Friday described Hariri as "a strong partner" and warned against "any party, within or outside Lebanon, using Lebanon as a venue for proxy conflicts or in any manner contributing to instability in that country".
This is a tumultuous time for Saudi Arabia.
Mr Hariri also defended his resignation. That may be an attempt to consolidate power before eventually inheriting the throne. It also told its citizens to leave Lebanon, and avoid all travel there.
He also repeatedly said he was ready to die for Lebanon - his father, former Prime Minister Rafik Hariri, was killed by a auto bomb in Beirut in 2005 - but added that he didn't want his children to go through that kind of ordeal.