Sunan Abi Dawud Book 2, Hadith 301
I saw Sharik who led us in the 'Asr prayer during a funeral ceremony. He placed his cap in front of him, that is, for saying the obligatory prayer the time of which had come.
The Prophet (ﷺ) said: ...... He then narrated the tradition about drawing the line.
Sufyan said: We did not find anything by which we could reinforce this tradition, and this has been narrated only through this chain.
He ('Ali b. al-Madini, a narrator) said: I said to Sufyan: There is a difference of opinion of the name (Abu Muhammad b. 'Amr). He pondered for a moment and then said: I do not remember except Abu Muhammad b. 'Amr Sufyan said: A man had come to Kufah after the death of Isma'il b. Umayyah ; he was seeking Abu Muhammad until he found him. He asked him (about this tradition) but he became confused. Abu Dawud said: I heard Ahmad b. Hanbal who was questioned many times how the line should be drawn. He replied: In this way. horizontally like crescent.
Abu Dawud said: I heard Musaddad say: Ibn Dawud said: The line should be drawn perpendicularly.
Abu Dawud said: I heard Ahmad b. Hanbal describing many times how the line should be drawn. He said: In this way horizontally in the round semi-circular form like the crescent, that is (the line should be) a curve.
The Prophet (ﷺ) used to pray facing his camel.