Is it valid to apply the saying, "If you continue doing something for 21 days, it will become a habit," to prayer in order to encourage people to pray, and to consider that committing to it for 21 days will make it a permanent habit?

Habits are acquired through persistence, and a Muslim is required to perform prayer as an act of worship that brings spiritual delight and inner peace. Allah may forsake someone who prays for years and then abandons it. So, whoever knows the virtue of prayer and the danger of abandoning it, and reflects on the names and attributes of Allah and the Hereafter, will maintain it. There is no harm in saying to someone who abandons prayer: "Bear yourself to it until it becomes familiar, for the delight of obedience is only attained through striving against the self." This is not limited by a specific period; whenever a servant is sincere in their striving, Allah's care will reach them and assist them. They should seek help by casting aside distractions, adhering to supplication, and keeping company with righteous people.