Mukhtasar Bukhari (Abridged) 665 — Standing for the funeral is Sunnah

Sayyiduna Amir bin Rabi’ah (may Allah be pleased with him) narrates from the Noble Prophet (peace and blessings of Allah be upon him) that he (peace be upon him) said: “When any one of you sees a funeral procession, if he is not accompanying it, he should stand up until it passes by him or before it passes by him or until it is placed down.”