Slaves were expected to perform grudgingly, only under fear of whipping, so when Joseph showed up whistling at his work, his boss was taken aback. Joseph made all the other slaves look bad because he did more work, did a better job, got things cleaner, cooked better. Whatever task he was assigned, he outdid expectations.
Eventually, Potiphar promoted him to managing director, in charge of his entire household.
As Christians, we should exceed expectations regularly. In our service in church, on outreach in the field, taking care of the needy of the world, we must strive for excellence and not offer a second-best or good-enough “sacrifice with blemish.”
At the end of 13 years of this trial, Joseph went from slave to vice president. God saw his faithfulness and excellent service and promoted him. We can expect good things if we exceed expectations.