Nietzsche actually wrote “that which does not kill us only makes us stronger”. But the rest of phrase is from the Bible. Nietzsche agreed with Jesus about finding where to find our core strength (being an athiest) and Jesus' teachings made it clear that there were a lot of things that made us weak after going through them. Like using hatred towards others to be safe or saving our material possesions from a fleeting world to protect ourselves from a life we have no control over. These to Jesus were signs of weekness, but not to Nietzsche.
Nietzsche actually wrote “that which does not kill us only makes us stronger”. But the rest of phrase is from the Bible. Nietzsche agreed with Jesus about finding where to find our core strength (being an athiest) and Jesus' teachings made it clear that there were a lot of things that made us weak after going through them. Like using hatred towards others to be safe or saving our material possesions from a fleeting world to protect ourselves from a life we have no control over. These to Jesus were signs of weekness, but not to Nietzsche.