In [*D'varim* 22][1], the [*pasuk* commanding placement of *tzitziyos*][2] on 4-cornered garments immediately precedes the [*pasuk* describing/commanding getting married][3]. The juxtaposition gave rise to the *minhag* of simultanaizing these two acts. 

(Extracting instructive meaning from the juxtaposition of two verses is [universally acceptable][4] as a method of interpretation only in *D'varim*. The example used by the *g'mara* to prove this includes one of the aforementioned *p'sukim*.)


  [1]: http://he.wikisource.org/wiki/%D7%93%D7%91%D7%A8%D7%99%D7%9D_%D7%9B%D7%91
  [2]: http://he.wikisource.org/wiki/%D7%A7%D7%98%D7%92%D7%95%D7%A8%D7%99%D7%94:%D7%93%D7%91%D7%A8%D7%99%D7%9D_%D7%9B%D7%91_%D7%99%D7%91
  [3]: http://he.wikisource.org/wiki/%D7%A7%D7%98%D7%92%D7%95%D7%A8%D7%99%D7%94:%D7%93%D7%91%D7%A8%D7%99%D7%9D_%D7%9B%D7%91_%D7%99%D7%92
  [4]: http://hebrewbooks.org/shas.aspx?mesechta=14&daf=4&format=pdf