As you can see the book of Abu Hamed Al-Ghazali. REVIVAL OF RELIGION'S SCIENCES (IHYA' ULUM AD-DIN) vol 3, page 169
He says:-as related by Ibn Abbas in the words of the Almighty: "And from the evil of Nightfall when it becomes dark." (Al-Falaq 3)
By this is meant the erection of the penis.
Alkarbala