Foot
      to foot or shoulder to shoulder?
Question

                While praying in
      congregation, should we stand foot to foot or shoulder to shoulder?
Praise be to Allah.The correct view is that in the rows of prayer, we should
    stand shoulder to shoulder and foot to foot.
Al-Bukhaari, may Allaah have mercy on him, narrated (683)
    from Anas that the Prophet 
 (peace and blessings of Allaah be upon him)
    said: “Make your rows straight, for I can see you from behind my back.”
Anas said: “so each of us would stand with his shoulder
    against his neighbour’s shoulder and his foot against his foot.”
Al-Bukhaari (may Allaah have mercy on him) gave this
    chapter the title: “Chapter on standing shoulder to shoulder and foot to
    foot.”
He said: al-Nu’maan ibn Basheer said: “I saw people
    standing with their ankles against their neighbours’ ankle.”
Shaykh ‘Abd al-‘Azeem al-Abaadi said: he said in al-Ta’leeq
    al-Mughni: These ahaadeeth clearly indicate the importance of making the
    rows straight, which is part of the perfection of prayer; they indicate that
    people should not stand back (from the row) or in front of (the row), and
    that they should stand shoulder to shoulder, foot to foot and knee to knee
    with their neighbours. But nowadays this Sunnah is being ignored! If someone
    does this nowadays the people shy away from him like zebras! Verily to
    Allaah we belong and unto Him is our return.
(‘Awn al-Ma’bood, 2/256)
The shoulder: is the place where the upper arm joins the
    body.
The ankle: is the bone which protrudes at the side of the
    foot.
And Allaah knows best.