الَّذِينَ يُؤْمِنُونَ بِالْغَيْبِ وَيُقِيمُونَ الصَّلَاةَ
Those who believe in the unseen and establish prayer. (Al-Baqarah 2:3)
The opening of Sūrat al-Baqarah presents characteristics of the God-conscious: belief in the unseen, establishing prayer, giving, and related qualities. The discourse then returns to these people by using «أُولٰئِكَ».
The sequence matters rhetorically: the qualities that ground their standing are mentioned first; guidance and success are then attributed to those very people. Without recognizing this relationship, the repeated reference and descriptive passage may look like unnecessary repetition.