a man whose appearance was like bronze: An angelic guide would lead Ezekiel's tour of the temple. The bronze color reminds us of the heavenly creatures described in the first vision (see Ezekiel 1:7).
Unlike the guide for his earlier vision of the earthly temple in Ezekiel 8–11, this guide carried only a linen measuring cord and a measuring rod. These are tools for building, not destroying.
Measurement is a key theme in the following chapters. It allows the prophet to emphasize the importance of certain parts of the temple by making them larger and more precisely defined than other parts.