God is spirit. Therefore, when He made us in His own likeness, He made us as spirits.
God is also eternal, and therefore as spirits made in His own likeness, our spirits are eternal, too.
Genesis 1:
26 Then God said, “Let Us make man in Our image, according to Our likeness;
And let them rule over the fish of the sea and over the birds of the sky and over the cattle and over all the earth, and over every creeping thing that creeps on the earth.”
27 God created man in His own image, in the image of God He created him; male and female He created them.
28 God blessed them; and God said to them, “Be fruitful and multiply, and fill the earth, and subdue it;
And rule over the fish of the sea and over the birds of the sky and over every living thing that moves on the earth.”
https://www.biblegateway.com/passage...1&version=NASB