1 א
שולחן ערוך, אבן העזר, כג:א
2 ב
It is forbidden to spill seed. This sin is more grievous than any other sin in the Torah.
[Translation by Rabbi Steve Greenberg]
3 ג
Time Period: Medieval (Geonim through the 16th Century)
Shulhan Aruch Even HaEzer 23:1