Rabada, who was at his fiery best with the ball on Thursday, had a sloppy moment on the field as he conceded an overthrow boundary in the 66th over of the day.
Kohli was all pumped up with the incident and he gave thumbs-up gestures all around the ground as the South Africa pacer walked away from the scene with head in floppy hat.
The official Facebook page of the Indian cricket team also uploaded the video of the incident with the caption: "For Laughs: An incident on the field got captain Virat Kohli smiling."
Rabada was pick of the South African bowlers as he scalped all the three Indian wickets that fell on the first day of the Test match. He got the wickets of Rohit Sharma, Mayank Agarwal and Cheteshwar Pujara as India ended the day at a score of 273/3, with Kohli and Ajinkya Rahane remaining unbeaten at the crease.