Rule 1: 1. 'A man who …': the clause after an indefinite noun
After an indefinite noun, a whole sentence can follow without any connecting word, and it serves as the description of that noun: رَأَيْتُ رَجُلًا رَكِبَ جَمَلًا I saw a man (who) rode a camel. If the noun is the object inside the clause, a pronoun suffix points back to it: جَمَلٌ كَانَ يَرْكَبُهُ a camel (that) he used to ride, literally a camel, he was riding it. The relative words used after definite nouns come later in the volume.
رَأَيْتُ رَجُلًا رَكِبَ جَمَلًا.
raʾaytu rajulan rakiba jamalan
I saw a man who rode a camel.
لِسَعِيدٍ جَمَلٌ كَانَ يَرْكَبُهُ إِلَى الْمَدِينَةِ.
li-saʿīdin jamalun kāna yarkabuhu ila-l-madīnati
Saʿīd has a camel that he used to ride to town.
كَانَ + imperfect: 'used to'.
فِي الْحَدِيقَةِ فِيلٌ يَأْكُلُ مِنْ يَدِ الْحَارِسِ.
fi-l-ḥadīqati fīlun yaʾkulu min yadi-l-ḥārisi
In the garden there is an elephant that eats from the keeper's hand.
سَأَلْتُ وَلَدًا كَانَ فِي الْقَرْيَةِ.
saʾaltu waladan kāna fi-l-qaryati
I asked a boy who had been in the village.
هٰذَا حِصَانٌ رَكِبْتُهُ الْيَوْمَ.
hādhā ḥiṣānun rakibtuhu-l-yawma
This is a horse that I rode today.
The suffix ـهُ on رَكِبْتُهُ refers back to حِصَانٌ.