because they had not met the Israelites with food and water, but had hired Balaam to call down a curse against them (although our God had turned the curse into a blessing).
Jewish Publication Society of America Version (JPS1917) - Nehemiah 13:2 >because they met not the children of Israel with bread and with water, but hired Balaam against them, to curse them; howbeit our God turned the curse into a blessing.