عصمة
ʿiṣma
The belief that God protected the prophets from major sin and from error in conveying His message.
What it means
Muslim scholars hold that prophets are preserved from lying, from hiding the message and from grave sins. The Quran speaks openly of their lapses: Adam’s slip (20:121), Moses striking a man (28:15–16), David’s test (38:24) and the Prophet’s frown at the blind man (80:1). Each is followed by repentance and forgiveness. They show that prophets are human, and teach how to return to God.
Term and Arabic as listed in Ismail al Faruqi, Toward Islamic English (International Institute of Islamic Thought, 1995), p. 39, listed as ʿIṢMAH. The definition is restated here.