What was the response of Prophet Muhammad (peace be upon him) when we greeted him while he was praying?
 Narrated `Abdullah:                     We used to greet the Prophet while he was praying and he used to answer our greetings. When we returned from An-Najashi (the ruler of Ethiopia), we greeted him, but he did not answer us (during the prayer) and (after finishing the prayer) he said, "In the prayer one is occupied (with a more serious matter)."