Lesson 3 of the Pali Primer

>Saddhim / saha meaning 'with' is also used with the instrumental
case. They are not normally used with nouns denoting things.< What
is the reason for useing Saddhim instead of Saha or Saha instead of
Saddhim? As below for example?

1. Samano narena saddhim gamam gacchati.
The monk goes to the village with the man.
2. Putto matulena saha candam passati.
The son sees the moon with his uncle.


Is there any thing in the following that indicate ownership(?) as in
his/theirs instead of "the"

1. Buddho savakehi saddhim viharam gacchati.The Buddha goes to the
monastry with the/his disciples

17. Sugato savakehi saha viharam agacchati.The Buddha comes to the
monastry with the/his disciples

20. Kumara assehi saddhim gamam dhavanti.The boys run to the village
with the/their horses

Thank-you
Mettena