Desiring to be teachers of the law; understanding neither what they say, nor whereof they affirm.
Sample of their 'vain talk.'
Desiring - would-be teachers; not really so.
The law - the Jewish law (Titus 1:14; Titus 3:9). The Judaizers in the letters to the Galatians and Romans made the works of the law necessary to justification, in opposition to Gospel grace. The Judaizers here corrupted the law with "fables" added on to it, subversive of morals as well as truth. Their error was not in maintaining the obligation of the law, but in ignorantly abusing it by fabulous and immoral interpretations.
Neither what they say, nor whereof - neither understanding their own asseverations nor the object about which they make them.