Let
and
be an Eisenstein series and a cusp form, respectively, of the same weight
and of the same level
, both eigenfunctions of the Hecke operators, and both normalized so that
. The main result we prove is that when
and
are congruent mod a prime
(which we take to be a prime of
lying over a rational prime
), the algebraic parts of the special values
and
satisfy congruences mod the same prime. More explicitly, we prove that, under certain conditions, \[ \frac{\tau (\bar{\chi })L(f,\chi ,j)}{(2 \pi i)^{j-1}\Omega _f^{\text{sgn}(E)}} \equiv \frac{\tau (\bar{\chi })L(E,\chi ,j)}{(2 \pi i)^{j}\Omega _E} \pmod{\mathfrak{p}} \] where the sign of
is
depending on
, and
is the corresponding canonical period for
. Also,
is a primitive Dirichlet character of conductor
,
is a Gauss sum, and
is an integer with
such that
. Finally,
is a
-adic unit which is independent of
and
. This is a generalization of earlier results of Stevens and Vatsal for weight
. The main point is the construction of a modular symbol associated to an Eisenstein series.