What was the sin whereby our first parents fell from the estate wherein they were created?

Answer

The sin whereby our first parents fell from the estate wherein they were created, was their eating the forbidden fruit ().

Read the 1 proof texts (KJV)

Genesis 3:6,12,16-17: ⁶And when the woman saw that the tree [was] good for food, and that it [was] pleasant to the eyes, and a tree to be desired to make [one] wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat. ¹²And the man said, The woman whom thou gavest [to be] with me, she gave me of the tree, and I did eat. ¹⁶Unto the woman he said, I will greatly multiply thy sorrow and thy conception; in sorrow thou shalt bring forth children; and thy desire [shall be] to thy husband, and he shall rule over thee. ¹⁷And unto Adam he said, Because thou hast hearkened unto the voice of thy wife, and hast eaten of the tree, of which I commanded thee, saying, Thou shalt not eat of it: cursed [is] the ground for thy sake; in sorrow shalt thou eat [of] it all the days of thy life;