What are the 善知识 (spiritual guides or friends) that we hear mentioned in the Buddhist Sutras?

#1

Master Sheng Yen gives his discourse on:
What does a “spiritual friend” mean?

Spiritual friends are both teachers and companions; they advise us, encourage us, and help us through their suggestions, through their association with us, and through their conceptual guidance. So, keeping a good friend, a spiritual friend near can develop character, increase wisdom, and facilitate peace of mind and body, a happy and harmonious family, and a smooth career.

#2

Venerable Ru Jun talks about why and how we should depend on 善知识 (spiritual guides) and their teachings.
And that we should seek out our spiritual guides.

Starting from the 7:00 minute mark:

#3

Venerable Ru Jun describes a story how Master Ri-Chang felt the suffering that pigs being brought to slaughter were going through and used this as motivation for himself. The pigs thus became Master’s spiritual guides.

listen from the 3:56 min mark: