The hadeeth: “Whoever sends blessings upon me once, Allah will send blessings upon him one thousand times”
Question

                How sound is this hadeeth? The Prophet (blessings and peace of Allah be upon him) said: “Whoever sends blessings upon him once, Allah will send blessings upon him one thousand times; whoever sends blessings upon him ten times, it will be light for him on the Day of Resurrection; whoever sends blessings upon him one thousand times perfectly, it will be the cause of intercession for him on the Day of Resurrection; whoever sends blessings upon him one thousand times every day will not be punished in his grave, even if his sins were like the foam of the sea”?
Praise be to Allah.
    We have 
    not found this hadeeth in any of the books of Sunnah that we have before us, 
    and we have not found it mentioned by any of the scholars, so it is not 
    permissible to attribute it to the Prophet (blessings and peace of Allah be 
    upon him). 

    What 
    appears to be the case is that it is falsely attributed to the Prophet 
    (blessings and peace of Allah be upon him). What is indicative of that is 
    the fact that it is contrary to that which is proven in saheeh reports. One 
    of the things that are proven in the saheeh Sunnah is that whoever sends 
    blessings upon the Prophet (blessings and peace of Allah be upon him) once, 
    Allah will send blessings upon him ten times in return, and not one thousand 
    times. It was narrated from ‘Abdullah ibn ‘Amr ibn al-‘Aas (may Allah be 
    pleased with him) that the Prophet (blessings and peace of Allah be upon 
    him) said: “whoever 
    sends blessings upon me, Allah will send blessings upon him tenfold”. 
    Narrated by Muslim (384). 

    What is 
    prescribed for the believer is to send a great deal of blessings upon the 
    Prophet (blessings and peace of Allah be upon him), as much as he can, 
    because of the great reward that will result from that in this world and the 
    Hereafter. 

    Shaykh Ibn 
    Baaz (may Allah have mercy on him) said: 

    Doing a 
    great deal of dhikr (remembrance of Allah), asking for forgiveness, and 
    sending blessings and peace upon the Messenger of Allah are among the 
    greatest means of attaining peace of mind and tranquillity in the heart, of 
    turning to Allah, may He be glorified and exalted, and finding comfort in 
    that, and of dispelling loneliness, unsteadiness and confusion. But there is 
    no set limit for asking for forgiveness or for sending blessings upon the 
    Prophet (blessings and peace of Allah be upon him). Rather what is 
    prescribed is to send a great deal of blessings and peace upon the Prophet 
    (blessings and peace of Allah be upon him) and not to define a set number, 
    and to ask for forgiveness a great deal, one hundred times, or more or less. 
    As for setting the number at one hundred, there is no basis for that. But 
    you should send a great deal of blessings upon the Prophet (blessings and 
    peace of Allah be upon him), standing or sitting, by night and by day, on 
    the road and at home, because Allah, may He be glorified and exalted, says 
    (interpretation of the meaning): “Allah 
    sends His Salat (Graces, Honours, Blessings, Mercy, etc.) on the Prophet 
    (Muhammad SAW) and also His angels too (ask Allah to bless and forgive him). 
    O you who believe! Send your Salat on (ask Allah to bless) him (Muhammad 
    SAW), and (you should) greet (salute) him with the Islamic way of greeting 
    (salutation i.e. As-Salamu Alaikum)” 
    [al-Ahzaab 33:56]. 
    And the Prophet (blessings and peace of Allah be upon him) said: “whoever 
    sends blessings upon me, Allah will send blessings upon him tenfold”. So do 
    that a great deal and be optimistic. There is no set limit; send blessings 
    upon the Prophet as much as you can, ten times, or more, or less, according 
    to whatever is easiest for you, without defining a set number. End quote. 
    Majmoo‘ Fataawa Ibn Baaz (11/209). 

    And Allah 
    knows best.