In recent years liberals have had much to say about the kinds of reasons that citizens should offer one another when they engage in public political debates about existing or proposed laws. One of the more notable claims that has been made by a number of prominent liberals is that citizens should not rely on religious reasons alone when persuading one another to support or oppose a given law or policy. Unsurprisingly, this claim is rejected by many religious citizens, including those who are also committed to liberalism. In this paper I revisit that debate and ask whether liberal citizens have a moral obligation not to explain their support for existing or proposed laws on the basis of religious reasons alone. I suggest that for most (ordinary) citizens no such obligation exists and that individuals are entitled to explain their support for a specific law and to persuade others of the merits of that law on the basis of religious reasons alone (though there may be sound prudential reasons for not doing so). My argument is grounded in the claim that in most instances advocating laws on the basis of religious reasons alone is consistent with treating citizens with equal respect. However, I acknowledge an exception to that claim is to be found when using religious reasons to justify a law also implies that the state endorses those reasons. For this reason I argue that there is a moral obligation for some (publicly influential) citizens, and especially those who hold public office, to refrain from explaining their support for existing or proposed laws on the basis of religious reasons. I conclude by suggesting that this understanding of the role of religion in public political discourse and the obligations of liberal citizens is a better reflection of our experience of liberal citizenship than that given in some well-known accounts of liberalism.