Thawab Al-A'mal- Sheikh Al-Sadouq p.146:
Ishaq Bin Ammar Al-Sayrafi said: "I was in Al-Koufa and many brothers would come to me. I hated notability and I was afraid of being famous for my religion, thus I ordered my servant to tell whoever comes asking for me that I am not here. I performed pilgrimage that year, so I met Abou Abdellah (pbuh) and noticed that there is a distance and change between us. Therefore, I said: "May I be sacrificed for you! What changed my position to you?" He (pbuh) said: "It is what you changed in your behavior with the believers." I said: "May I be sacrificed for you! I was only afraid of being famous, yet Allah knows how great my love for them is." He (pbuh) said: "O Ishaq, do not stop visiting your brothers, for when a believer meets his faithful brother and says hello, Allah shall continue recordinga greeting for him until the Day of Resurrection and if he shakes his hand, Allah shall send down between their thumbs a hundred mercies, ninety nine for the one who has stronger love for his friend. Allah shall come to them as well and He shall be closer to that of them who has stronger love for his friend. Moreover, if they hug, mercy shall embrace them. If they stay together, not desiring anything of this earthly world but Allah, they shall be told: 'You have been forgiven, so go on.' If they begin to discuss a matter of their own, the angels will say to one another: 'Move away from them, for they are speaking of a secret and Allah has concealed it.'" He (pbuh) said: "Ishaq." I said: "May I be sacrificed for you! Will not our words be recorded? For Allah Almighty said: "Not a word will be spoken without being recorded by a designed keeper." The son of the Messenger of Allah (pbuhp) took a deep breath and then wept until his tears drenched his beard and said: "O Ishaq, Allah, the All-Blessed the Most High, orders the angels to leave the believers when they meet out of honor for them. If the angels do not record their utterances and do not know their words, He Who keeps them, the Knower of the secrets and what is concealed has known them. O Ishaq, fear Allah as if you can see Him. You do not see Him, yet He sees you. If you believe that He does not see you, then you have disbelieved and if you know that He sees you and then you conceal your sins from people and reveal them to Him, then you have made Him the least observer you take notice of.""
Thawab Al-A'mal- Sheikh Al-Sadouq p.184:
Abou Hamza reported from Abou Abdellah (pbuh) that he said: "When you shake hands, you gain as the rewards of the Strivers (Mujahids)."
Al-Kafi- Sheikh Al-Koleini vol.2 p.180:
Malik Al-Jahni reported that Abou Jaafar (pbuh) said: "O Malik, you are our Shia. Do you not see that you are neglecting our matter! Allah cannot be described and as Allah cannot be described, we cannot be described as well. As we cannot be described, a believer cannot be described as well. When a believer meets another believer and shakes hands with him, Allah shall continue to look at them and sins will be shed from their faces like leaves are shed from trees until they separate. Thus, how can who is like this be described?"
Al-Kafi- Sheikh Al-Koleini vol.2 p.183:
Abou Jaafar and Abou Abdellah (pbut) said: "If any believer left his house to visit his brethren, knowing his rights, Allah shall record for him for every step he took a good deed, erase and bad deed and raise him to a higher rank. When he knocks on the door, the doors of the sky will be opened for him. When they meet, shake hands and hug one another, Allah shall come to them and then He will show pride in them before the angels. Thus He will say: "Behold My servants.They visited one another and loved each other. They deserve not to be tormented in Hell after this incidence." When he departs, angels, equal to the number of his breaths, stepsand words will accompany him, and protect him from earthly ordeals and the calamities of the Hereafter until that night comes again. So if he dies in between, he will be exempted from judgment and if the visitor's right was known (to the visited) as the visitor knew the right of the visited, he would have gained the same rewards."