All three of the world's major monotheistic religions traditionally affirm that petitionary prayers can be causally efficacious in bringing about certain states of affairs. Most of these prayers are offered before the state of affairs that they are aimed at helping bring about. In the present paper, I explore the possibility of whether petitionary prayers for the past can also be causally efficacious. Assuming an incompatibilist account of free will, I examine four views in philosophical theology (simple foreknowledge, eternalism, Molinism, and openism) and argue that the first three have the resources to account for the efficacy of past-directed prayers, while the latter does not. I further suggest that on those views which affirm the possible efficacy of past-directed petitionary prayers, such prayers can be ‘impetratory’ even if the agent already knows that the desired state of affairs has obtained.