This is the 9098th most frequent Russian word.
саидом
"Саидом" is the instrumental case of "Саид," a proper name, meaning "by Said" or "with Said."
In this sentence, 'саидом' refers to the proper noun, 'Said', showing instrumental case usage which indicates the action of 'meeting with Said'.
Мы встретились с Саидом вчера на концерте.
We met Said yesterday at the concert.
In the third example, 'саидом' signifies accompaniment, showing the instrumental case function of indicating 'together with Said'.
Мы решили пойти в музей вместе с Саидом.
We decided to go to the museum together with Said.
Here, 'саидом' is used to describe a personal interaction with Said, again employing the instrumental case to highlight association.