Kumar exploited the green conditions underfoot by getting the ball the seam across Elgar.
New batsman Hashim Amla was also tested with the remaining three balls from Bhuvneshwar, but survived the rest of the over.
Bhuvneshwar, though, gained further success when he trapped
Aiden Markram (5) in his second over lbw.
The big news at the toss, though, was
Batsman Temba Bavuma was the unfortunate casualty, with all-rounder Andile Phehlukwayo making way for the return of captain Faf du Plessis.
Teams For Newlands
South Africa: Dean Elgar, Aiden Markram, Hashim Amla, AB de Villiers, Faf du Plessis (captain), Quinton de Kock, Vernon Philander, Keshav Maharaj, Kagiso Rabada, Dale Steyn, Morné Morkel.
India: Murali Vijay, Shikhar Dhawan, Cheteshwar Pujara, Virat Kohli (captain), Rohit Sharma, Wriddiman Saha, Hardik Pandya, Ravichandran Ashwin, Mohammad Shami, Bhuvneshwar Kumar, Jasprit Bumrah.