“Things are not permanent” – Not even teachings. Teachings are expedient means. From Zen Marrow talk II

If one is a student of Guo Gu’s or has observed his teaching method(s), one will realize that he teaches for the moment. He gives his students what they need at a particular point in time.  He interacts with students differently and may even interact with the same student in a different way. Part of learning is to do and hear things in a variety of ways.

Language tends to cement actions and thoughts. If one’s thoughts are cemented or cased in stone, one has difficulty learning or hearing.

There are an idiom and song lyric that goes: ”Different strokes for different folks.”