The error in the sentence "He told to me that he was leaving" lies in the use of the preposition "to" after the verb "told." The verb "tell" is a transitive verb, which means it directly takes an object (the person being told) without needing a preposition like "to." The correct construction is simply "He told me."
In contrast, the verb "say" often requires "to" when followed by an indirect object (the person). For example, you would say "He said to me that he was leaving." However, with "tell," the direct object immediately follows the verb. Therefore, including "to" makes the phrase redundant and grammatically incorrect.
The correct sentence should be: "He told me that he was leaving." Understanding this distinction between "tell" and "say" is crucial for accurate and natural English sentence construction, ensuring proper verb usage and avoiding common grammatical mistakes related to prepositions.