it actually means that It is a human weakness. Shaitan runs in the blood of human beings. Muhammad's shaitan became a Muslim,(he said it) it means it can't call him towards evil. Khata (mistake) is not a evil/sin, just mishap. No prophet of God is exempt from Shaitan. These are human weaknesses. Vision of Hadhrat Moses (as) while traveling along the sea coast when the fish got lost. He said Shaitan made him forget it.