Galatians and 1 Thessalonians advances the interpretation of these letters by exploring how the Apostle Paul quotes, alludes to or "echoes" the Jewish Scriptures and other ancient materials. Comparative wording is at the forefront, whether in relation to Abraham, Sarah, Hagar, or prophecies and promises from Genesis, Habakkuk, Isaiah, Jeremiah, Ezekiel, the Psalms, or other texts such as Philo. Issues and controversies include such topics as faith (ἐκ πίστεως), the Torah, the Holy Spirit, holiness, suffering, eschatology, allegorical interpretation, identity of the Israel of God, Zion and the return from exile, Roman piety, imperialism, and hidden transcripts.