Well the condition will be different for each component. Resonance doesn't matter. The current must obviously be identical in all three series elements. The Voltage across the resistance will be in phase with that current, and the Voltage across the capacitance must lag the current by 90 degrees, while the Voltage across the inductance must lead the current by 90 degrees. This makes the inductance and capacitance Voltages 180 degrees out of phase. At resonance they will be equal and opposite, so they cancel leaving just the whole source Voltage across the resistance.