It is narrated from Hazrat Abu Hurairah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: There is absolutely no "aghrar" in prayer and salam. Imam Ahmad (may Allah have mercy on him) says that I asked Abu Amr al-Shaibani (may Allah have mercy on him) about the meaning of this hadith, so he said that the word is not "aghrar" but "gharar," and according to Imam Ahmad (may Allah have mercy on him), the meaning of "gharar" is that a person should not exit from the prayer until he has complete certainty that the prayer has been fully completed, and as long as he thinks that some part of the prayer remains, he should not leave the prayer.