The reason why brothers in the faith shake hands is Allah's love for them. The Messenger of Allah said, 'Whenever brethren shake hands in Allah, their wrong actions are dispersed so that they become as they were on the day their mothers bore them.' No two brothers' love and respect for each other increases without there being increase for each of them also. It is obligatory for the one having most knowledge of Allah's faith among the two to stimulate his friend to perform the obligatory functions which Allah has made necessary, and to guide him in going straight, in contentment and moderation, to give him the good news of Allah's mercy and to make him fear His punishment. The other brother must seek the blessing of his guidance and hold to what he calls him to, adhere to his admonition, and be guided by him, all the while seeking protection in Allah and seeking His help and success.
‘Isa (‘a) was once asked, 'How are you this morning?' To which he replied, 'I do not possess the benefit which I hope for, nor can I repel what I am on my guard against, while I am commanded to obey and forbidden to rebel. I do not think that any pauper is poorer than I am.' And when Uways al-Qarani was asked the same question, he said, 'How is a man in the morning when he does not know if he will be alive in the evening, and in the evening he does not know if he will be alive in the morning?'
Abu Dharr said, 'In the morning I thank my Lord and I thank myself.' The Holy Prophet said, 'Whoever wakes up in the morning aspiring for something other than Allah has become among the losers and transgressors.'