This (the Hebrew version of it) is a commonly used phrase in rabbinic literature. It refers to the concept that a true hypothesis will tend to have - by virtue of its being true - corroborating evidence.
The earliest source of this statement that I can find in rabbinic literature is a 12th Century Biblical commentator. But I wonder if this is taken - or paraphrased - from the works of some earlier (Non-Jewish) source.
Anyone familiar with this?