פירוש על בבא קמא 54:5

We don't collect "knas" in Bavel - - It (this payment) is not a "knas" - it is a "din knas". It says in "Hachovel" (later on - Chapter 4, 84:) that the courts in Bavel do not have the same amount of power as the courts in Israel [because they (the courts in Bavel) are an] extension [of the courts in Israel].