There are ways for someone who has distanced himself from religion to come back, the best of them to explain to him are:
1. Make him understand that the blessings given to us by Allah from the creation to all the other blessings are a proof of Allah’s love for us. So, why should we leave Allah? And, if Allah takes these blessings away from us one day, would we or anyone else be able to get them back or create them over again? In addition, is Allah’s purpose behind sending prophets and religion anything else then letting man reach success? Psychologists say that it is a given that most psychological illnesses and mental diseases are found in irreligious people with weak will power and no interest in spiritualism. Alexis Carol, the author of a psychological book about humans being unknown writes that man can achieve great strength through prayer. She says that in her expertise she saw people without any hope saved by the strength of prayer. Man can increase his limited strength by grasping a limitless source. Therefore, is it rational for one to run away from success? Is running away from success anything other than failure?
2. If his sense of religion has been polluted with sin he must take the path that the teachers of ethics have prescribed: purifying one’s soul by putting conditions on oneself, protecting oneself from disobeying those conditions, and accounting how one did. One should put a condition on himself that he will not commit a sin then he should protect himself from committing the sin and then account for what he did so he can realize the mistakes he made and in the end be able to leave them. A person who is after something by sin will loose more than he gains and will be in trouble regarding the things that he lost.
3. If his environment, bad friends is the reason that he has left religion he should think rationally, he should know that friends that take him away from Allah are not after his interests.
4. If one left religion because the rules are too hard of limiting it must be said to him that Allah is out for our interests and although we do not know the wisdom behind the rules we consider them hard and limiting. This is similar to a mother and father forbidding their child from playing with dangerous items; this forbiddance is limiting for the child and seems difficult, but in reality it is in his interests.
5. If one left religion because of the stubbornness of people around him the people around him must invite him to religion with love and must refrain from cutting ties or treating him harshly.
For more information refer to the following sources:
1. Tanhā’ī Lidhat wa ‘Ashq by ‘Alī Asghar Zuhayrī
2. Purshishā wa Pasukhhā, v.9 by the representatives of the Walī al-Faqīh
3. 40 Hadīth, Imām Khomeini
4. Mīzān al-Hikmah
5. Hikmathā wa Andarzhā by Shahīd Muttahariī