Text Classification with NO model training

NLP (Natural Language Processing) is the field of artificial intelligence that studies the interactions between computers and human languages, in particular how to program computers to process and analyze large amounts of natural language data. NLP is often applied for classifying text data. Text classification is the problem of assigning categories to text data according to its content. In order to carry out a classification use case, you need a labeled dataset for machine learning models training. So what happens if you don't have one?