What is the source of the Kallah circling the Chasan 7 times?
The Kallah encircles the Chosson seven times under the chuppah, from the verse "A woman shall go around a man." (Jeremiah 31:22)The act also recalls the seven times Tefillin straps are wrapped around The arm. Just as a man binds himself in love of Hashem, so is his bond in love to the Bride. The number seven represents the completion of the seven day process in which earth was created. During these seven days, the earth revolved on its axis seven times. Since marriage reenacts the creative process, the Kallah's encirclement symbolizes the repetition of these seven rotations.The Chosson is compared to a king. Just as the king is encircled by his legion, the groom is to be encircled by his bridal entourage.
Summarized from:Jewish Wedding Traditions