The sentence is grammatically correct. Here's why:
* Subject-Verb Agreement: The subject "gift" is singular, and the verb "is" agrees with it.
* Tense: The verb "had given" is in the past perfect tense, which is appropriate because it refers to an action that happened before another past action (receiving the gift).
* Sentence Structure: The sentence follows a simple subject-verb-object structure.
However, it's important to note that the sentence can be interpreted in a few ways.
* Literal Meaning: The sentence literally states that grammar is the most precious gift you've received from God.
* Figurative Meaning: It could be a humorous or ironic statement about the importance of grammar.
Ultimately, the meaning of the sentence depends on the context and your intended message.