legal standard of the day -- when could workers recover wages in 1840s pennsylvania

The ruling here established the fact that "faithful service" is an agreement implicit in the employment contract. That is to say, if a worker "misbehaves" on the job, he is not legally entitled to any back pay (e.g., if he misbehaves on the 29th of the month and the employer fires him promptly and wages for the month are due to him on the 30th, he gets nothing). From Libhart v. Wood (PA, 1841) argued before the Supreme Court of Pennsylvania:

When a servant, who has engaged for a certain time at certain wages, is turned away by his master before the period for which he has engaged to serve has expired, and his dismissal be in consequence of his own misconduct, he will be entitled to no wages; for his faithful service is a condition precedent to his right to wages, and that condition, in the case supposed, he has not performed. But if his dismissal be unjust, the master can not, by his wrongful discharge, prevent the servant from recovering a compensation for his services. Thus the law carefully protects the rights of both master and servant.