Scholiast on Apollonios Rhodios, Argonautika 3.467
According to the hymns of Orpheus Hekate was a daughter of Deo; according to Bacchylides, a daughter of Nyx; according to Musaeus, a daughter of Zeus and Asteria; and according to Pherecydes, she was a daughter of Aristaios.

Pausanias, Description of Greece 2.30.2
Of the Gods, the Aiginetans worship most Hekate, in whose honour every year they celebrate mystic rites which, they say, Orpheus the Thracian established among them. Within the enclosure is a temple; its wooden image is the work of Myron, and it has one face and one body. It was Alkamenes of Athens, in my opinion, who first made three images of Hekate attached to one another.

Proem of the Orphic Argonautika
When driven by the goad of Kings Bakchos and Apollon, I described their terrible shafts, and likewise I disclosed the cure for feeble mortal bodies and the Great Rites to initiates. Truly, above all I disclosed the stern inevitability of ancient Chaos, and Time, who in his boundless coils, produced Aether, and the twofold, beautiful, and noble Eros, whom the younger men call Phanes, celebrated parent of eternal Night, because he himself first manifested. Then, I sang of the race of powerful Brimo, and the destructive acts of the giants, who spilled their gloomy seed from the sky begetting the men of old, whence came forth mortal stock, which resides throughout the boundless world. And I sang of the service of Zeus, and of the cult of the Mother and how wandering in the Cybelean mountains she conceived the girl Persephone by the unconquerable son of Kronos, and of the renowned tearing of Kasmilos by Herakles, and of the sacred oath of Idaios, and of the immense oak of the Korybantes, and of the wanderings of Demeter, her great sorrow for Persephone, and her lawgiving. And also I sang of the splendid gift of the Kabeiroi, and the silent oracles of Night about Lord Bakchos, and of the sea of Samothrace and of Cyprus, and of the love of Aphrodite for Adonis. And I sang of the rites of Praxidike and the mountain nights of Athela, and of the lamentations of Egypt, and of the holy offerings to Osiris. And also I taught the multitudinous ways prophesying: from the motion of wild birds and from the positions of entrails; how to receive the prophetic dreams that pierce the mind in sleep, and the interpretation of signs and omens and what the motion of the stars means. I taught atonement that brings great happiness for mortals; and how to supplicate the gods and give offerings to the dead. And I described that which I gained by sight and thought when on the dark way of entering Haides via Taenaron, relying on my cithara, through the love of my wife. And I described the sacred test of the Egyptians in Memphis that is used to convey prophesy, and the sacred city of Apis, which is surrounded by the river Nile.

Orphic Argonautika 122 ff
After I came to the enclosures and the sacred place, I dug a three-sided pit in some flat ground. I quickly brought some trunks of juniper, dry cedar, prickly boxthorn and weeping black poplars, and in the pit I made a pyre of them. Skilled Medeia brought to me many drugs, taking them from the innermost part of a chest smelling of incense. At once, I fashioned certain images from barley-meal [the text is corrupt here]. I threw them onto the pyre, and as a sacrifice to honor the dead, I killed three black puppies. I mixed with their blood copper sulfate, soapwort, a sprig of safflower, and in addition odorless fleawort, red alkanet, and bronze-plant. After this, I filled the bellies of the puppies with this mixture and placed them on the wood. Then I mixed the bowels with water and poured the mixture around the pit. Dressed in a black mantle, I sounded bronze cymbals and made my prayer to the Furies. They heard me quickly, and breaking forth from the caverns of the gloomy abyss, Tisiphone, Allecto, and divine Megaira arrived, brandishing the light of death in their dry pine torches. Suddenly the pit blazed up, and the deadly fire crackled, and the unclean flame sent high its smoke. At once, on the far side of the fire, the terrible, fearful, savage goddesses arose. One had a body of iron. The dead call her Pandora. With her came one who takes on various shapes, having three heads, a deadly monster you do not wish to know: Hekate of Tartarus. From her left shoulder leapt a horse with a long mane. On her right should there could be seen a dog with a maddened face. The middle head had the shape of a lion [or snake] of wild form. In her hand she held a well-hilted sword. Pandora and Hekate circled the pit, moving this way and that, and the Furies leapt with them. Suddenly the wooden guardian statue of Artemis dropped its torches from its hands and raised its eyes to heaven. Her canine companions fawned. The bolts of the silver bars were loosened, and the beautiful gates of the thick walls opened; and the sacred grove within came into view. I crossed the threshold.

Orphic Hymn 1. To Hecate
Lovely Hecate of the roads and crossroads I invoke;
In heaven, on earth, and in the sea, saffron-cloaked,
Tomb spirit, reveling in the souls of the dead,
Daughter of Perses, haunting deserted places, delighting in dear,
Nocturnal, dog-loving, monstrous queen,
Devouring wild beasts, ungirt, of repelling countenance.
You, herder of bulls, queen and mistress of the whole world,
Leader, nymph, mountain-roaming nurturer of youth, maiden,
I beseech you to come to these holy rites,
Ever with joyous heart and ever favoring the oxherd.