The toga in which Caesar had been slain played a mighty emotional and religious role.
The conspirators used it as a signal for the bloody assassination. While dying Caesar hid his violated face in it. At his funeral it decisively elicited a major change.
The blood stained toga never left the people's imagination and it eventually mutated to the Holy Shroud.
Suetonius, Divus Iulius, 81.1-2, 84.1
Plutarchus, Marcus Brutus, 20.3
Plutarchus, Julius Caesar, 66.6, 66.12
Nicolaus Damascenus, Vita Augusti, 24
Cassius Dio, Historia Romana, 19.4
Appianus, Bella Civilia, 2.117, 2.146
Quintilianus, Institutio Oratoria, 6.1.31