$\forall$$a$, $b$, $c$:ES, $P$:(${\it es}$:ES$\rightarrow$E$\rightarrow\mathbb{P}$).
\\[0ex]$a$ $\equiv$ $b$ mod ${\it es}$,$e$.$P$(${\it es}$,$e$) $\Rightarrow$ $b$ $\equiv$ $c$ mod ${\it es}$,$e$.$P$(${\it es}$,$e$) $\Rightarrow$ $a$ $\equiv$ $c$ mod ${\it es}$,$e$.$P$(${\it es}$,$e$)