Ruling on member of the congregation leaving straight after the imam says the salaam
Question

                When the congregational prayer ends and the salaam has been said at the end of the prayer, when can the member of the congregation move? Can he move before the imam turns around, or must he wait and not move before him?.
Praise be to Allah.Once the imam has said the 
    salaam, it is permissible for the person who prayed behind him to move, 
    whether the imam has turned to face the congregation or has stayed where he 
    is, or he has got up from his place. But it is better for the person who 
    prayed behind him to stay put until the imam turns to face the congregation, 
    because of the possibility that the imam may be sitting so that he can do 
    the two prostrations of forgetfulness (sujood al-sahw) after saying the 
    tasleem at the end of the prayer. Even better than this is to get up only 
    after the imam has got up. 
There is an indication that 
    it is permissible to leave as soon as the salaam has been said in the report 
    narrated by al-Bukhaari (875) from Umm Salamah (may Allaah be pleased with 
    her) who said: When the Messenger of Allaah  (peace and blessings of 
    Allaah be upon him) said the salaam, the women got up when he finished his 
    tasleem and he stayed in his place for a while before getting up. One of the 
    narrators of the hadeeth said: We think, and Allaah knows best, that this 
    was so that the women could disperse before any of the men caught up with 
    them. 
With regard to the report 
    narrated by Muslim (426) from Anas (may Allaah be pleased with him) who 
    said: The Messenger of Allaah  (peace and blessings of Allaah be upon 
    him) led us in prayer one day, and when he had finished praying he turned to 
    face us and said: “O people, I am your imam, so do not go ahead of me in 
    bowing, prostrating, standing or finishing, for I can see you from in front 
    of me and behind me,” what is meant by “finishing” here is the salaam. 
Al-Nawawi (may Allaah have 
    mercy on him) said: The words of the Prophet  (peace and blessings of 
    Allaah be upon him): “so do not go ahead of me in bowing, prostrating, 
    standing or finishing” indicate that it is haraam to do these things and 
    others that are similar to them. What is meant by finishing is the salaam. 
    End quote. 
Imam al-Shaafa’i (may 
    Allaah have mercy on him) said in al-Umm (1/151): The one who has 
    prayed behind an imam may leave when the imam has finished the salaam, 
    before the imam gets up, and he may delay that and leave after the imam 
    leaves, or leave with him, which I like better. End quote. 
Ibn Qudaamah (may Allaah 
    have mercy on him) said in al-Mughni (1/328): It is mustahabb for the 
    one who has prayed behind an imam not to get up and leave before the imam, in case he remembers something that he forgot and does the prostration of forgetfulness. End quote. 
And Allaah knows best.