Two conditions for the leader of any people
In the next verse (24), it was said:
وَجَعَلْنَا مِنْهُمْ أَئِمَّةً يَهْدُونَ بِأَمْرِنَا لَمَّا صَبَرُوا ۖ وَكَانُوا بِآيَاتِنَا يُوقِنُونَ
(And We appointed leaders from among them who guided (people) under Our command, when they observed patience, and kept firm belief in Our verses).
In this verse, two reasons have been given as to why religious leadership was bestowed on some of the sages of Bani Isra'il: (1) Observance of patience and (2) the certitude of Divine words. In terms of the Arabic usage, the sense of doing sabr or patience is very wide and general. Literally, it means to tie or to be firm. At this place, sabr means to stay firm on the implementation of Divine injunctions and to hold one's desiring self in check against the infringement of what Allah Ta'ala has declared to be Karam (unlawful) or makruh (reprehensible). This covers one's obedience to all injunctions of the Sharl'ah which is pragmatic perfection at its best. The second reason lies in their certitude - they are certain of the Divine words. This includes the initial understanding of the sense of the verses as well as the resulting certitude which emerges from such comprehension - both. This is intellectual perfection at its best.
In short, in the sight of Allah Ta’ ala, only those who are perfect both in 'ilm (knowledge) and 'amal (practice) are worthy of religious leadership. It is interesting here that perfection in practice has been made to precede perfection in knowledge while, usually 'ilm (knowledge) precedes ` amal (practice). This arrangement releases a strong hint, that is, a knowledge which has no corresponding practice with it is just not credible in the sight of Allah.
Ibn Kathir has reported the following saying of some ` Ulama' in his tafsir of this verse:
بِالصَّبرِ وَ الیَقِینِ تُنَالُ الِا مَا مَۃُ فِی الدِّینِ
One can arrive at the station of leadership in religion only through sabr (patience) and yagin (certitude).