Resuming on 139 for five in reply to Pakistan's 338, AB de Villiers and Dean Elgar added a further 25 runs before the latter became Saeed Ajmal's sixth victim of the innings.
Left-hander Elgar (23) flashed at a tossed-up delivery that gripped on the surface and caught the edge, flying to Younus Khan at slip. It was a disappointing end for a player looking to cement a permanent spot in the South African test side with JP Duminy on the road to recover from an Achilles injury.
Robin Peterson joined de Villiers at the crease and the pair pushed up the scoring rate as they attacked the bowling, taking risks that were rewarded.
Pakistan took the new ball as soon as it was available, ending a marathon spell of 35 consecutive overs in the innings from Ajmal, and it brought them a wicket.
De Villiers and Peterson had added 46 for the seventh wicket in 11 overs with the former reaching his 32nd half-century before he became the first test wicket for Mohammad Irfan.
De Villiers (61) tried to place a leg-side delivery through mid-wicket, but was too early into the shot and spooned the ball to Umar Gul at mid-on.
Peterson (40 not out) and Vernon Philander (11 not out) were together at the interval on a pitch that is taking turn, but still looks good for batting. – Reuters