Amin Aḥsan Islahi writes in his exegesis, Tadabbur-i Quran in reference to Quran 20:124:

There is a vacuum in a human being which is only filled by faith in God. So unless he has this faith in him nothing else can give him peace of mind and assurance. Other things, however grand and attractive they may be, can provide temporary joy but they cannot give relief to the anxiety found in the heart and soul of a person. When a child cries because of hunger, it can be appeased for a little while through a nipple or a soother but it receives satisfaction only when a mother feeds it. Without this arrangement, the child remains restless. Similar is the case with a human being. He may provide himself with various means and resources but if he is deprived of faith in God he will remain dissatisfied, hesistant, fearful, unstable and in a state of spiritual crises however much he may try to hide this. The kingdom of the satisfied soul is acquired by true and firm faith. اَلَا بِذِكْرِاللّٰهِ تَطْمَئِنَّ الْقُلُوْبُ (Listen! It is only through God’s remembrance that hearts receive assurance).A question may arise here: there are many people who lay claim to faith but they spend their lives in great worries and straitened circumstances; on the other hand, there are so many who regard faith in God to be a hoax but they lead very comfortable and happy lives. The answer to this question is that in the first place here the discussion is not with those who merely lay claim to faith but with those who have true faith. Secondly, we only see the apparent splendour of those whom we regard to be very happy even though they are indifferent to God. If we were able to creep into their hearts, we would be able to see so many threats, doubts and fears concealed in them but they are not apparent to everyone. Only they themselves can see them or those who have the insight of faith in them.