Emily Manong died of injuries she suffered in the attack.
Manong was giving testimony to the commission's human rights violations hearing in Beaufort West in the Karoo.
His mother's house was first attacked by United Democratic Front-affiliated youths in August 1985, and she had to flee the township.
Later the youths said she could return home, but in November that year her house was attacked again.
Six other people were injured in the attack and were taken to the G J Kempken Hospital in Victoria West, where Emily died of her wounds.
Her last words were: "This time they have me, but they have not broken my spirit," Manong said.
The attack took place at a time of political upheaval in the area. A number of people were arrested in connection with the attack, but they were all acquitted.
Manong testified he had become a born-again Christian, and had come to terms with what had happened to his mother. He did not however want to discuss the incident with her alleged attackers, saying he would find this "very difficult" and preferred to leave the situation as it was.