The one who says this first gets 90 good deeds.
السَّلَامُ عَلَيْكُمْ
When you shake hands with a muslim brother, pray durood sharif and say :
يَغْفِرُاللهُ لَنَاوَلَكُمْ
It is narrated in the hadith sharif that when two muslim brothers shake hands and recite durood sharif, before their hands are separated, Allah Ta’ala forgives both of them.