Al-Sha'bi (may Allah have mercy on him) says that the Messenger of Allah (peace and blessings be upon him) said: "After me, let no one lead the prayer as imam sitting."
Ali bin Umar (al-Daraqutni) said: No one narrated it except Jabir al-Ju'fi, and he is matruk (abandoned). The hadith is mursal, and it cannot serve as proof.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5075