سنن ابن ماجه

Busr bin Sa’eed said: “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."