"Our information was he was going to be out of that (hospital) yesterday late or today," Gwede Mantashe, general secretary of the ruling ANC told reporters.
"So we are expecting him out today."
He said party officials had ordered Zuma on Friday to take a break because "the punishing election programme was taking its toll, not on him only, (but) on many of us".
Zuma's office said the 72-year-old leader checked into hospital yesterday for "tests" adding doctors were "satisfied" with his condition.
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The presidency on Friday said Zuma would take "a few days off from public engagements".
"We are expecting him to rest more," said Mantashe, without giving full details.
Zuma's next scheduled public appearance is on June 19 when he is due to deliver the state of the nation address in parliament.
He was sworn in for a fresh term two weeks ago after his African National Congress (ANC) party won the May 7 elections with an overwhelming 62 per cent of the vote.