Kane, HISTORY OF THE DHARMA ŚĀSTRA, VOL. II PART I, p. 82, Bhandarkar Oriental Research Institute, Poona 1941
has this:
<<...the practice current in the times of the Vedānta-sūtras that the Śūdra is not entitled to study the Veda.
Gaut. XII.4 went so far as to prescribe:—
‘if the śūdra intentionally listens for committing to memory the Veda, then his ears should be filled with (molten) lead and lac; if he utters the Veda, then his tongue may be cut off; if he has mastered the Veda his body should be hacked'.>>
Hoping it's of some help,
Regards,
Artur Karp