One of the few joys left to the slaves was their

religion

Explanation:

On their day of rest, the slaves would often escape to the woods for their own service. Sometimes the women would wet quilts and hang them from the branches. This would help muffle the sounds of their service. The slaves' services were lively.

Many of the slaves found their religion gave them a chance to open their hearts and express their deepest longings. Their worship offered them a breath of hope. One of the few joys left to the slaves was their religion