Opposition parties brought the case against Zuma to the Constitutional Court, whose proceedings in a packed, brick- lined chamber were shown on live television.
Opposition protesters marched to the courthouse as the robed judges inside considered whether the president broke the law by failing to follow a 2014 recommendation from the state watchdog agency that he pay back some of the more than USD 20 million in home upgrades.
"He didn't do what the constitution required him to do," said Wim Trengrove, a lawyer for the opposition. On February 3, Zuma's office said he was willing to reimburse some money.
His critics said he was trying to avoid the embarrassment of a court hearing about his conduct. The Constitutional Court was expected to clarify whether recommendations made by the Public Protector's office, which scrutinises state officials and institutions, are binding.
Zuma's presidency did not appear to be under immediate threat. Parliament has the power to remove him, but the ruling African National Congress party has a comfortable majority and has been supportive of his stance in the scandal over his private compound, known as Nkandla.