Jesus is sent out by Mary to play. He is snubbed by a group of rich boys. He builds "a bridge with the beams of the sun," and the boys who follow him across fall into the river and drown. Mary beats her child with a withy branch
It should perhaps be noted that this event has no place in the Bible, nor even in the (known) apocryphal gospels (though it reminds one of various events in the "Infancy Gospel of Thomas," which also contains some rather nasty miracles; Leather also mentions this obscure and vicious piece). The bridge of sunbeams is a commonplace in religious art.
Belden sees a connection between this song and the folk legend "Jesus and Joses," in which Joses (Jesus's brother; cf. Mark 6:3) tattles on Jesus and Jesus is beaten with willow twigs. There is a fundamental difference, however: In "The Bitter Withy," Jesus is genuinely guilty; in "Jesus and Joses," he is said to be innocent.
According to Leather, the local title "The Sally Twigs" came about because, in Hereford, a willow wand is called a "sally twig." The phrase is not used in either text she prints.- RBW