The mystical power to procreate:
The ability to have children is one of the greatest miracles embedded within nature, experienced and felt by every father and mother especially by the birth of their first child. This physical ability to procreate, and create something so magnificent from practically nothing, is the result of G-d’s infinite light, known as the Or Ein Sof, which carries the sole ability to create ex-nihilo. This infinite light of G-d is drawn down on Yom Kippur and is responsible for the forgiveness and atonement of one’s sins, as sin cannot blemish this light of G-d, and hence from this perspective it is as if sin does not exist. This same infinite divine light is drawn down on the day of the wedding for the sake of giving the couple the ability to procreate and have children. It is this very infinite light which then also provides atonement and forgiveness for all of one’s sins on the day of the wedding.
 See Toras Menachem 12:152, and Shulchan Menachem 1:158; The Chassidishe Parsha Likkutei Sichos Parshas Vayishlach