The Prophet (sal-Allaahu 'alayhe wa sallam) said: "Whoever sends a prayer upon me, Allaah sends ten upon him."  He (sal-Allaahu 'alayhe wa sallam) also said: "Do not take my grave as a place of habitual ceremony. Send prayers upon me, for verily your prayers reach me wherever you are."  He (sal-Allaahu 'alayhe wa sallam) also said: "The miser is one whom when I am mentioned to him, fails to send prayers upon me."  He (sal-Allaahu 'alayhe wa sallam) said: 'Allaah has Angels who roam the earth and convey salaam to me from my ummah.'  He (sal-Allaahu 'alayhe wa sallam) also said: ''Whenever someone sends salaam upon me, Allaah returns my soul to me so that I may return salaam to that person. 
 Muslim 1/288 No. 384.  Abu Dawud 2/218 No. 2044; Ahmed 2/367 No. 8804. Albani graded it as Sahih in Sahih Abu Dawud 2/363  At-Tirmithi 5/551 and others. See also Al-Albani, Sahih At-Tirmithi 3/177 and Sahihul-Jarai' As-Saghir 3/25.  An-Nasa'i, Al-Hakim 2/421. Al-Albani graded it authentic in Sahih An-Nasa'i 1/274.  Abu Dawud (no. 2041). Al-Albani graded it good in Sahih Abu Dawud 1/383.