Does "which is void of formations (conditioned phenomena) since it is the cessation of them" refer to nibbana or the knowledge that abides in nibbana?

The essay *The Progress of Insight* includes the following definitions: > [Maturity Knowledge](http://www.accesstoinsight.org/lib/authors/mahasi/progress.html#ch6.14) > Immediately afterwards, a type of knowledge manifests itself that, as it were, falls for the first time into Nibbana, which is void of formations (conditioned phenomena) since it is the cessation of them. This knowledge is called "maturity knowledge." > [Path Knowledge](http://www.accesstoinsight.org/lib/authors/mahasi/progress.html#ch7.15) > It is followed immediately by knowledge that abides in that same Nibbana, which is void of formations since it is the cessation of them. This is called "path knowledge." It is also called "purification by knowledge and vision." In the first paragraph, does “which is void of formations (conditioned phenomena) since it is the cessation of them” refer to nibbana, or does it refer to the knowledge that abides in nibbana?