“This day is holy to the Lord your God; do not mourn or weep.” For all the people wept as they heard the words of the Law. Then he said to them, “Go your way. Eat the fat and drink sweet wine and send portions to anyone who has nothing ready, for this day is holy to our Lord. And do not be grieved, for the joy of the Lord is your strength.”
Perhaps these words ring empty, particularly when considering world conflict or personal disappointment. When facing sorrowing circumstances, the last thing we want to hear is “Stop crying. Be happy.”
However, there are two ways to read this: as a prohibition (“do not”) or as an encouragement (“do not keep grieving”). I take this as the latter.
Elsewhere we know that Jesus cried, that we should weep with those who weep, etc. So there is a time to mourn, but this passage is meant to encourage those in sorrow. In other words, your sadness is justified (because of this sinful world), but do not remain in your sorrow (because comfort comes from God).
What suggests that reading is this: The people were weeping when hearing the law, which they should have done because of their sin. However, because it was a holy day, they were then told to not keep weeping but to celebrate God’s grace.