The affix ya comes in the sense of 'collection thereof' after the words 1. khala 2 go and 3. ratha,
Thus खल्या, गव्या and रथ्या ॥ These three words have not been included in the पाशादि class, in order that rule 4.2.51 should apply to them.,
खल-गो-रथात्
Adhyāya 4 · Pāda 2 · Rule 50