Labor certification must be granted before an employer qualifies to submit form I-129. Perhaps the employer meant that he was simultaneously filing form I-129 and proof of labor certification.
That will depend on when the I-129 was filed.Quoting sukumarps07
It would be a huge gamble to start working before receiving a receipt from the USCIS. He cannot start working in the new job until after form I-129 is received by the USCIS, and if he has no receipt he has no way of knowing if in fact the form was properly submitted or if it was rejected as improperly filed.Quoting sukumarps07
Keep working for his current employer. If that's not possible, no receipt is in hand, and returning home isn't an option, consult an immigration lawyer.Quoting sukumarps07

