Why is the diversity of tongues among the signs of God?

The intended meaning of the "variation in tongues" in the verse from Surat Ar-Rum is the diversity of languages spoken by people, and this is a grace from Allah Almighty to His servants. Allah has inspired every group of people with a language by which they communicate and has enabled them to articulate it. Ibn Al-Jawzi interpreted it as the variation in tones and voices, so much so that the voice of two brothers would not be confused, and this too is among the signs of Allah.