l is substituted for the r of gṝ in the intensive.,
Thus निजेगिल्यते, निजेगिल्येते, निजेगिल्यन्ते ॥ The root गॄ takes यङ्, when the sense of contempt is conveyed, with regard to the action denoted by the root, 3.1.24. गर्हितं गिलति = जेगिल्यते ॥
Some say that ग्र of the sutra includes the two roots गॄ (गिरति Tudadi 117) and गॄ (गृणाति Kryadi 28). Others hold that the Tudadi gri is only taken and not the Kryadi. The Kryadi gri never takes the Intensive form, no example of which is to be met in literature.
Why do we say in the Intensive? Observe निगीर्यते with the Passive affix यक् ॥,