After jumping through the time and space dimension to find Obito, Uchiha Madara confronts Obito who still held in possession one of his Rinnegan Eye’s. In order for Madara to awaken his third eye, he would need both Rinnegan eyes and the Sage of the Six Paths power from all 9 bijuus. Obito was still immobilized so Madara taking his eye back was no problem.
At the end of Manga Chapter 676, Madara decides to step up his power in his battle against Naruto, Sasuke, Sakura and Kakashi by opening his third eye called the Infinite Tsukuyomi.
Artwork by X7 Rust