«بَلْ» لِتَدَارُكِ الْغَلَطِ بِإِقَامَةِ الثَّانِي مَقَامَ الْأَوَّلِ
Bal corrects an error by placing the second expression in the position of the first.
The speaker first says one thing and then supplies a different expression as the intended account. However, the particle's grammatical function is not always identical to its legal effect.
A mere report may admit correction. A legal act that became effective when uttered may not be undone by a later correction. The interpreter must therefore first determine the status of the earlier words.