straight from the horse's mouth

「掛け値なしの／真実の」。昨日に続いて馬。馬は歯を見れば年がわかるというのはlook the gift horse in the mouthという表現で話しましたが、今日の表現も同じ根拠から来ています。誰がなんと言おうと、口の中を見ればその馬の年がわかる、つまり、ごまかしようのない情報、ということ。

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Finally, a few whispers straight from the horse's mouth.

This implies that there have been many rumors that were baseless.  There is no verb in this sentence.