It is unlucky to turn back after starting to go anywhere. To avert misfortune after turning back, make the sign of the cross in the dust with the heel, and spit in the cross.
Arkansas (negro), and Kentucky.

It is unlucky to turn back after starting to go anywhere. To avert misfortune after turning back, make the sign of the cross in the dust with the heel, and spit in the cross.
Source: Current Superstitions (1896), entry 1272.
Fanny D. Bergen, editor.
Modern normalized navigation; the historical attribution above remains unchanged.