How a Buddhist gets any new information regarding the teaching? There are three basic groups of inputs: own experience stemming from own practice, information from textual sources (scriptures of Buddhism, other texts on Buddhism, Dhamma), information from authoritative people (Buddhist teachers, Sangha). Regardless how we first learnt of Dhamma the three sources sooner or later appear in everyday life of the person.
Finding a right balance between them is extremely important. I have seen so many extremities like accepting only the word of the Teacher and not practicing at all or accepting only the word of the Teacher, practicing but never reading any suttas. Or only practicing and drawing all conclusions from the practice only. Or any other combinations of one or two sources from the three.
Using only one or two sources creates various delusions, hamper or completely stops the progress on the Path to Enlightenment. A teacher may make mistakes. A textual source may be interpreted incorrectly. Own practice may be delusive by itself. Sometimes all three are used but not equally.
I believe it is important to make use all of them and use equally. Whatever your practice produce should be questioned and verified against texts (suttas) and words of Teachers. Whatever you hear from a Teacher should be questioned and verified against suttas and own practice. Whatever you read in a sutta should be questioned and verified against two other. Then we reach a truly balanced approach and build a strong foundation for moving down the Path.