«سَلَّمْتُ عَلَى الطَّالِبِ الَّذِي قَرَأْتُ كِتَابَهُ» — I greeted the student whose book I had read.
«سَلَّمْتُ»: verb + subject; «عَلَى الطَّالِبِ»: prepositional phrase; «الَّذِي»: modifier of «الطَّالِبِ» in a genitive position.
«قَرَأْتُ»: verb + subject of the ṣilah; «كِتَابَهُ»: accusative object, with possessive «هُ» returning to the relative noun.
The verbal ṣilah itself has no independent iʿrāb position.