Jacob Zuma told South Africa's parliament on Thursday he had received no payments from private companies or individuals during his time as president, as opposition lawmakers walked out in protest over the cost to the state of his legal fees.
Allegations by government and opposition politicians that the wealthy Gupta family of businessmen used a friendship with Zuma to control state businesses and influence appointments are among many scandals that have dogged his presidency.
The Guptas and Zuma have denied any wrongdoing and say they are victims of a politically motivated witch-hunt.
"My government is committed to fighting corruption," Zuma said in response to a question.
He also said he would establish a judicial commission to investigate allegations made in a 2016 report by South Africa's corruption-fighting Public Protector.
"I did not receive any payments from private individuals or companies during my tenure as president of the Republic of South Africa, other than those disclosed or reported to the necessary authorities," he said in answer to another question.
The main opposition party then walked out of the session, saying Zuma was refusing to answer questions on how much the state had spent on legal fees to fight corruption allegations against him.
Democratic Alliance leader Mmusi Maimane had asked how much had been spent since May 1, 2009, to defend 783 corruption charges against Zuma that were dropped by the National Prosecuting Authority (NPA) before he ran for the presidency.
"He is going to jail. The president is going to jail," Maimane shouted before leading the walkout.
South Africa's High Court reinstated the charges last year and the Supreme Court upheld that decision in October, rejecting an appeal by Zuma. The 75-year-old president is still trying to prevent the NPA from filing the charges.
The "State of Capture" report by the Public Protector, whose job is to uphold standards in public life, recommended a judicial probe into allegations of systemic corruption by Zuma, some of his ministers and heads of state-owned companies.
But the president filed an application asking the High Court to set aside the report, saying he would instead set up a judicial commission of inquiry into the allegations. The court is expected to rule on that case soon.
Zuma told parliament the judicial commission would investigate those corruption allegations and any others brought to its attention.
"After the [High Court] judgment, I will establish it immediately. We will prove the lies and the truths," Zuma said. "The truth will be found."
The report focused on allegations that Zuma's friends, the businessmen and brothers Ajay, Atul and Rajesh Gupta, had influenced the appointment of ministers, which Zuma and the Guptas have denied.