What is the concept of belief in divine decree and destiny (Al-Qada' wal-Qadar)?

Everything in this universe is predestined and inscribed, and it does not change. However, this does not mean abandoning beneficial actions or hesitating. Rather, a person must be resolute and rely on Allah, striving for what benefits them, while realizing that Allah has ordained destinies with their causes. And what Allah has decreed is unseen to humans, so it is not permissible to rely on destiny while neglecting to take the means.