The reaction e+e− → HZ∗ is used to search for the standard model Higgs boson in the and the Hℓ+ℓ− channels. The data sample corresponds to about 4.5 million hadronic Z decays collected by the ALEPH experiment at LEP from 1989 to 1995 at centre-of-mass energies at and around the Z peak. Three candidate events are found in the Hμ+μ− channel, in agreement with the expected background from the electroweak process e+e−. This search results in a 95% C.L. lower limit on the Higgs boson mass of 63.9 GeV/c2.