Pietism was a 17th century Lutheran theological movement emphasizing private religious study and kindness. Now, Kant was raised in a pietist household and enrolled in pietist schools. So is there any parallel between his moral philosophy and pietist teachings?
▻ PIETISTIC INFLUENCE IN GENERAL TERMS
It is useful finally to remember that Kant grew up in the pietistic-eclectic, anti-Wolff ian milieu of Koenigsberg.41 The emphasis on free will, on the role of conscience, and the general moral pessimism which characterize pietism furnished the basis upon which the rational-demonstrative meth ods of dogmatic philosophy were criticized. The idea of a duty to believe in what, he insisted, cannot and should not be proved, was the basis of the moral philosophy of Crusius, whose influence on Kant in this connection has yet to be adequately explored.42 For a proof cannot substitute for the inner discipline of the subject, his recognition of an authority higher than himself which morality requires. But this conviction poses a problem of philosophical communication. How do you employ methods which are rational but non-demonstrative to persuade your reader, not that he lives in a world regulated by Providence, or indeed that any other proposition is the case, but to submit himself to this moral discipline? Clearly this cannot be done directly, for any such effort only leads to circularity from the standard, demonstrative point of view. Kant cannot prove that the form of morality is deontological rather than based in clannishness and sympa thy, unless he can prove that God exists, while, according to the surface scheme of his presentation, he cannot prove that God exists unless morality really does take this form. (Catherine Wilson, 'Interaction with the Reader in Kant's Transcendental Theory of Method', History of Philosophy Quarterly, Vol. 10, No. 1 (Jan., 1993), 83-97 : 93-4.
▻ FINESSING THE PIETISTIC INFLUENCE
To descend a level of detail, you might find the following article of use :
Dennis Vanden Auweele, 'The Lutheran influence on Kant's depraved will', International Journal for Philosophy of Religion, Vol. 73, No. 2 (April 2013), 117-135.
Here is an extract from the article, which makes relevant discriminations within pietism.
Kant was actually raised in Pietism, not Lutheranism or Calvinism. Pietism is a theological movement within Lutheranism which is usually, in the constructivist understanding (cf. Wallmann (1990), taken to be initiated by Philipp Jakob Spener (1635-1705) and continued by August Hermann Francke (1663-1727). Several scholars (cf. Lindberg (2005) point towards the earlier influence of Johann Arndt (1555-1621), Johannes Tauler (1300-1361) and Thomas à Kempis (1380-1471) on the movement. Within Pietism, two sub-movements emerged: Moravianism and Halle Pietism, of which the latter influenced Kant the most. (Auweele, 118 footnote 3.)