The courtship of Inanna and Dumuzi is one of the oldest love poems from the ancient world. It is a story of love between the gods (although some argue that Dumuzi was a real person, who rose to power, and so attained mythical divine status). When the gods consummate their love the result is fedundity on earth, particularly for their worshippers.
This Sumerian text is often compared to the Song of Songs. The Egyptian love poetry makes a better parallel, but there are some connections. However, this is much more explicitly sexual than the Song, and, of course, it is about divine lovers.
Here it is:
The brother spoke to this younger sister
The Sun God, Utu, spoke to Inanna, saying:
'Young Lady, the flax in its fullness is lovely,
Inanna, the grain is glistening in the furrow.
I will hoe it for you, I will bring it to you
A piece of linen, big or small, is always needed.
Inanna, I will bring it to you.'