Now I know my ABCs, won't you come and golf with me?
Vim, 42, 40 keystrokes/bytes
:h&lt;_&lt;cr&gt;jjYZZP:s/./&amp;, /g&lt;cr&gt;7f r&lt;cr&gt;9;.3;.3;.$ch.

Thanks to Lynn and her awesome vim answer for the tip to grab the alphabet from help.
Thanks to RomanGräf for saving two bytes!
Explanation:
:h&lt;_&lt;cr&gt;                                      &quot; Open up vim-help
        jj                                    &quot; Move down two lines
          Y                                   &quot; Yank this line (containing the alphabet)
           ZZ                                 &quot; Close this buffer
             P                                &quot; Paste the line we just yanked
              :s/./&amp;, /g&lt;cr&gt;                  &quot; Replace every character with that character followed by a comma and a space
                            7f                &quot; Find the seven space on this line
                               r&lt;cr&gt;          &quot; And replace it with a newline
                                    9;        &quot; Repeat the last search (space) 9 times
                                      .       &quot; Repeat the last edit (replace with a newline)
                                       3;     &quot; Third space
                                         .    &quot; Replace with newline
                                          3;  &quot; Third space
                                            . &quot; Replace with newline

Then, we move the end of the of the line with $, change back a character with ch and insert a dot.