"Ninsun, (even though) I am extraordinarily strong(?) … I must now travel a long way to where Humbaba is, I must face fighting such as I have never known, and I must travel on a road that I do not know! … intercede with Shamash on my behalf!" (3.23-31)
Check out one of the typical features of pantheistic belief-systems: just like in the Classical epics of Homer or Virgil, characters in The Epic of Gilgamesh exploit divisions between the different gods. Here, Gilgamesh asks his mom Ninsun to put in a good word for him with Shamash, the sun-god. But, before you interpret this as meaning that Gilgamesh is religious and wants the gods on his side, remember that Humbaba was created by Enlil and put in the Cedar Forest on purpose to terrify humans. Thus, while Gilgamesh wants one god to back him up, he is also getting himself in a conflict with another god, Enlil. In a world like this one, can a man—or a king—ever be on everybody's good side?
Ninsun went into her living quarters. She washed herself with the purity plant, she donned a robe worthy of her body, she donned jewels worthy of her chest, she donned her sash, and put on her crown. She sprinkled water from a bowl onto the ground. She … and went up to the roof. She went up to the roof and set incense in front of Shamash, she offered fragrant cuttings, and raised her arms to Shamash. (3.35-45)
Here we see that Ninsun listens to the prayers of her son, to put in a good word with Shamash. But, weirdly enough, she doesn't seem to have a special hotline to him, nor does she look him up in the top-secret gods-only telephone directory. Instead, she has to pray to him too, in much the same way that Gilgamesh prayed to her (his own mother).
Chapter 4, Tablet 4
Gilgamesh climbed up a mountain peak, made a libation of flour, and said: "Mountain, bring me a dream, a favorable message from Shamash." Enkidu prepared a sleeping place for him for the night; a violent wind passed through so he attached a covering. He made him lie down, and … in a circle. They … like grain from the mountain … (4.8-14)
These lines come from Gilgamesh and Enkidu's voyage to the Cedar Forest. Here, we get a hint at the special religious importance that Mesopotamian culture attached to dreams, which were often seen as prophesying the future or as messages from the gods. Just another way that religion was part of everyday life.
"Hurry, stand by him so that he (Humbaba) does not enter the forest, and does not go down into the thickets and hide (?)! He has not put on his seven coats of armor(?), he is wearing only one, but has taken off six." (4.225-234)
And all those prayers to Shamash pay off. When Enkidu and Gilgamesh finally reach the Cedar Forest, Gilgamesh has a moment of doubt. But then Shamash himself speaks out of the heavens, telling him to cheer up—and to strike now, while Humbaba is vulnerable. This is the first of several times that Shamash will personally intervene to help out Gilgamesh and Enkidu. Gee, must be nice to have a personal sun-god.
Chapter 5, Tablet 5
Enkidu spoke to Gilgamesh, saying: "My friend, Humbaba, Guardian of the Forest, grind up, kill, pulverize(?), and … him! Before the Preeminent God Enlil hears, and the … gods are full of rage at us. Enlil is in Nippur, Shamash is in Sippar. Erect an eternal monument proclaiming … how Gilgamesh killed(?) Humbaba." (5.241-248)
Hey, Enkidu! Aren't you grateful? Did you forget that Shamash has been helping you out the whole time? Enkidu clearly isn't thinking straight here. And he'll pay for it later on, when Enlil insists he must die for killing Humbaba, and chopping down the mightiest tree in the Cedar Forest. If you're going to act against the will of the gods, you'd better be ready to take the punishment.
Chapter 6, Tablet 6
After they had killed the Bull of Heaven, they ripped out its heart and presented it to Shamash. They withdrew, bowing down humbly to Shamash. Then the brothers sat down together. Ishtar went up onto the top of the Wall of Uruk-Haven, cast herself into the pose of mourning, and hurled her woeful curse: "Woe unto Gilgamesh who slandered me and killed the Bull of Heaven!" When Enkidu heard this pronouncement of Ishtar, he wrenched off the Bull's hindquarter and flung it in her face: "If I could only get at you I would do the same to you! I would drape his innards over your arms!" (6.147-157)
This is probably the poem's clearest example of how, in the polytheistic culture of ancient Mesopotamia, people weren't just abstractly "religious." Instead, they had personal relationships with a variety of gods. Some gods would be their friends, but some could even be their enemies. Here, Enkidu and Gilgamesh continue to act as devoted worshippers of Shamash, the god who helped them out throughout their quest against Humbaba. On the other hand, Enkidu really goes nuts on Ishtar—surpassing even Gilgamesh's behavior, earlier on, when he insulted and rejected her.
Chapter 8, Tablet 8
When Gilgamesh heard this the zikru of the river(?) he created … Just as day began to dawn Gilgamesh opened(?) … and brought out a big table of sissoo wood. A carnelian bowl he filled with honey, a lapis lazuli bowl he filled with butter. He provided … and displayed it before Shamash. (8.222-228)
The text of the tablet is broken in a few places here, and scholars don't know how to translate one of the words ("zikru"). (Sissoo trees, however, are actually a thing.) Still, the general idea seems to be that Gilgamesh is making an offering to Shamash before setting out on his journey to find Utanapishtim. If your personal god is a dude like Shamash, that's a relationship you want to keep up.
Chapter 10, Tablet 10
"How alike are the sleeping(?) and the dead. The image of Death cannot be depicted. (Yes, you are a) human being, a man(?)! After Enlil had pronounced the blessing, the Anunnaki, the Great Gods, assembled. Mammetum, she who fashions destiny, determined destiny with them. They established Death and Life, but they did not make known 'the days of death.'" (10.302-309)
Here, Utanapishtim tries to show Gilgamesh that death is a sacred limitation ordained by gods.When Gilgamesh finally backs down from his quest, are his reasons religious? If not, what are they?
Chapter 11, Tablet 11
"Then I sent out everything in all directions and sacrificed (a sheep). I offered incense in front of the mountain-ziggurat. Seven and seven cult vessels I put in place, and (into the fire) underneath (or: into their bowls) I poured reeds, cedar, and myrtle. The gods smelled the savor, the gods smelled the sweet savor, and collected like flies over a (sheep) sacrifice." (11.155-171)
Here, Utanapishtim explains what he did after the Flood. At first glance, this looks like a straightforward picture of the "you-scratch-my-back, I'll-scratch-yours" relationship that is typical between mortals and gods in ancient mythology. Utanapishtim gets the sacrifices in order, and the gods gratefully cluster round. But, um, didn't the gods just try to kill everyone?