Why would Ancient Egyptians believe in a God known as Heket, that has the head of a frog ?

 In Ancient Egypt when the River Nile floods, the river bank is inundated with frogs, they were spontaneously generated in the fertile mud left behind after the water receded, Frogs have a magical connection to the spiritual world of Egyptians, frog spawn looks like an egg conceived in the human womb

The Goddess Heket with a human body and a frog's head was the  goddess of fertility, and was associated with pregnancy and childbirth, she is  the consort of Khnum, the potter god, who would sculpt and create  models of the human body using the rich mud of the River Nile. 

Heket has the power to bring body and spirit into the being. Together with her consort Khumn they were  responsible for the formation, creation, and birth of every living being in the Egyptian universe.  Heqet would  breath  Ka into an inanimate being, Ka, in ancient Egyptian religion, was the soul of a human being or of a god, it was endowed with all the person’s qualities and faults. The ka is a spiritual double that lives on even after the death of the physical self.  Once Heket has invoked the Life force, the child is placed in the mother’s womb

It was common for pregnant women to wear amulets which portrayed the goddess Heqet for protection. The Priestesses who worked in the Mammsi houses ('place of giving birth') and helped with childbirth are known as 'the Servants of Heket'. Hekhet could bring on labour and offer her protection during labour. Khnum created the physical body, Heqet helps souls enter it. Just as the rebirth of a physical body, Heqet’s knives are used to severe the binding cords   

Heket and Khumn were portrayed on the walls In Birth rooms, birth colonnades and Mamsi houses. On the Birth Colonnade at Hatshepsut's Mortuary Temple at Dier El Bahari,  it is  recorded that Hatshepsut was the child of the God Amun with her mother the Queen Ahamose.  Heket holds an ankh to the nostrils of the  infant Hatshepsut and her ka, the ankh represents the breath, life, and spirit, it is a potent symbol representing the union of male and female and earth and heaven  It offers the gift of immortality, Hatshepsut does not expire or exhale, but inhales the breath of life. The Ankh represents the concept of Eternal Life.  The Ankh offers the body life and spiritual healing and protection against bad energies

The relief’s  on Hatshepsut's birth colonnade portray that it was the divine intention of both her  earthly father Tuthmosis 1, and her heavenly father Amun that she would rule Egypt, In the birth Colonnade it declares:

‘Amen –Ra called for the God Khumn the Creator and Fashioner of the Bodies of Men.’ Fashion for me the body of my daughter and the body of her Ka, a great queen shall I make of her, and honor and power shall be worthy of her dignity and glory’  ‘Amun-Ra answered Khumn ‘It shall be done as you have said.  So Khumn fashioned the body of Amen-Ra’s daughter and the body of her Ka, the two forms exactly alike, and more beautiful than the daughters of men. He fashioned them with clay from the air of his potters wheel and Heqet goddess of birth with the frogs head, knelt by his side holding the sign of life towards the clay that the bodies of Hatshepsut and her Ka might be filled with life and breath, and so one of the greatest queens of Egypt was announced to the world. 

In the Birth room at Luxor Temple I circled around the outside of the barque shrine and walked through a doorway that led into a suite of rooms that represent the bedroom of Amun where the Opet festival rituals took place, the pharaoh would  retire to the Birth Room, from which he would later  emerge symbolically re-born and restored. The statues of the king’s ka were no longer on display because the ka was now believed to have taken residence in the pharaoh’s body.  Reliefs in the birth room represent Amon choosing the Queen Mutemweje to give birth to his son. He sent Thoth with the message to the queen and ordered Khnum to create an image of himself on his potter’s wheel. The boy child Amenophis was born into the world created by Amon and then crowned as the King. I realized the similarity of this sequence of events of this ancient Egyptian relief as it compares to our Christmas story of the angel coming to visit Mary to tell her that she will give birth to the son of God.    As the Royal scribe Ani said; ‘God reveals himself in millions of forms’

Heket is present at both conception and death of a body, she is also shown in the afterlife tomb scenes as when death arrives, Heqet cuts the bindings that life places on the soul and stands guard to guide the body into the afterlife.