“When anyone of you performs prayer, let him put something in front of him. If he cannot find anything then let him put a stick. If he cannot find one, then let him draw a line. Then it will not matter if anything passes in front of him.”
Sunan Ibn Majah Book 5, Hadith 141
← Previous Hadith “The Messenger of Allah had a reed mat that he would spread out during the day, and make into a compartment at night, towards which he would perform prayer.”

Sunan Ibn Majah Book 5, Hadith 140 Next Hadith → “They sent me to Zaid bin Khalid to ask him about passing in front of one who is performing prayer. He told me that the Prophet (ﷺ) said: ‘Waiting for forty is better than passing in front of one who is performing prayer.’”

(One of the narrators) Sufyan said: "I do not know if he meant forty years, months, days, or hours."

Sunan Ibn Majah Book 5, Hadith 142