Joy is an attribute of perfection. Hence the Lord Most High is described as possessing its highest and most perfect forms. His joy at a person’s repentance, for example, is greater than the joy of someone who recovers his mount, carrying his food and drink, in a deadly wilderness after losing it and despairing of ever finding it again.
The point is that joy takes various forms: the heart’s bliss, delight, and gladness. Joy and happiness are its bliss, while anxiety and sorrow are its torment. Rejoicing in something goes beyond being content with it: contentment brings the heart reassurance, tranquillity, and openness, whereas joy brings it delight, gladness, and happiness. Everyone who rejoices is content, but not everyone who is content rejoices. Thus joy is the opposite of sorrow, while contentment is the opposite of displeasure. Sorrow pains the one who experiences it, whereas displeasure does not, unless accompanied by an inability to exact revenge. And Allah knows best.
[Surah Yūnus (10): verse 87]
“We revealed to Moses and his brother: ‘Take houses for your people in Egypt, make your houses places of prayer, establish prayer, and give good tidings to the believers.’” (87)
This is among the finest and most masterful examples of composition. The address begins in the dual, since Moses and Aaron were the two messengers who were to be obeyed. The Children of Israel were equally obliged to obey each of them. When the two provided houses for their people, their people followed their lead.
Then the pronoun shifts to the plural in “establish prayer,” because establishing it is obligatory upon everyone. It then shifts to the singular in “give good tidings to the believers,” because Moses was the principal messenger, while his brother was his support and minister. Just as Moses held the principal role in the mission, he also held the principal role in conveying good tidings.
Furthermore, since Moses and his brother were sent with a single message, they constituted a single messenger, as in His words, 26:16: “Indeed, we are the messenger of the Lord of all worlds.” It is this messenger who was told: “Give good tidings to the believers.”