Правило 78 Василия Великого

Let the same statute be observed for those who take two sisters together, even if it was at different times. (Ap. 19; Trul. 26, 54; Neokes. 2; Basil the Great. 23, 87; Theophila Alex. 5). Anyone who marries the sister of his first wife is also subject to fifteen years of penance. See about this in the interpretation of rule 87 of the same holy father. You might be interested in: