Should he say the adhaan if he wants to pray on his own in the mosque?
Question

                If I have missed the prayer in congregation and I am in the mosque, should I say the adhaan or just the iqaamah?.
Praise be to Allah.
    The scholars are agreed that the one who enters the mosque 
    and prays alone does not have to say the adhaan or iqaamah, and that the 
    adhaan and iqaamah of the muezzin in the mosque are sufficient for him. 

    Imam al-Shaafa’i (may Allaah have mercy on him) said in 
    al-Umm (1/106): 

    I do not know of any disagreement with the view that if a 
    person comes to the mosque when the imam has finished praying, he may pray 
    without any adhaan or iqaamah. End quote. 

    It is mustahabb for him to say the iqaamah before beginning 
    to pray, and it is best if he says the adhaan and iqaamah, because the 
    adhaan and iqaamah are dhikr or remembrance of Allaah. This idea was 
    indicated by Qataadah (may Allaah have mercy on him) when he said: Nothing 
    but good will come to you from testifying that there is no god but Allaah 
    and that Muhammad is the Messenger of Allaah. 

    It is proven that Anas (may Allaah be pleased with him) 
    entered the mosque when they had finished praying, and he told a man to say 
    the adhaan and iqaamah. Narrated by al-Bukhaari in a mu’allaq report and by 
    Ibn Abi Shaybah in al-Musannaf (1/250). Classed as saheeh by 
    al-Albaani in Tamaam al-Minnah (p. 150). 

    Sa’eed ibn al-Musayyab said concerning people who came to the 
    mosque when the prayer had ended: they should say the adhaan and iqaamah. 
    This is the view of Imam al-Shaafa’i (may Allaah have mercy on him). 

    See: Mughni al-Muhtaaj (1/318) and al-Nawawi in 
    al-Majmoo’ (3/93). 

    Ibn Qudaamah said in al-Mughni (2/74): It is better 
    for each worshipper to say the adhaan and iqaamah, unless he is making up a 
    missed prayer or at a time other than the time of the adhaan, in which case 
    he should not say it out loud. End quote. 

    i.e., so that he will not confuse the people with his 
    adhaan. 

    He also said (2/79): 

    If a person enters the mosque where the prayer has already 
    been offered, if he wishes he may say the adhaan and iqaamah. This was 
    stated by Ahmad. 

    And if he wishes he may pray without any adhaan or iqaamah, 
    because ‘Urwah said: If he comes to the mosque when the people have already 
    prayed and said the adhaan and iqaamah, then their adhaan and iqaamah will 
    suffice for those who come after them. This is the view of al-Hasan, 
    al-Sha’bi and al-Nakha’i, but al-Hasan said: It is better, in their view, to 
    say the iqaamah. 

    If he says the adhaan it is mustahabb for him to say it 
    quietly and not out loud, so that the people will not be confused by an 
    adhaan that is given at a time other than the usual time. End quote. 

    See also the answer to question no.
    5660 and
    6130. 

    And Allaah knows best.