  We analytically calculate the dominant two-loop electroweak correction, of
O(G_F^2 m_t^4), to the partial width of the decay of a Higgs boson, with mass
M_H << m_t, into a bottom-quark pair, and describe the most important
conceptual and technical details of our calculation. As a by-product of our
analysis, we also recover the O(alpha_s G_F m_t^2) correction. Relative to the
Born result, the O(G_F^2 m_t^4) correction turns out to be approximately
+0.047% and, thus, more than compensates the O(alpha_s G_F m_t^2) one, which
amounts to approximately -0.022%.
