We present a search for the standard model Higgs boson produced in association with a Z boson in 4.2 fb−1 of p¯p collisions, collected with the D0 detector at the Fermilab Tevatron at √s=1.96 TeV. Selected events contain one reconstructed Z→e+e− or Z→μ+μ− candidate and at least two jets, including at least one b-tagged jet. In the absence of an excess over the background expected from other standard model processes, limits on the ZH cross section multiplied by the branching ratios are set. The limit at MH=115 GeV is a factor of 5.9 larger than the standard model prediction.Received 20 August 2010DOI:https://doi.org/10.1103/PhysRevLett.105.251801© 2010 The American Physical Society