I desire therefore that men pray everywhere, lifting up holy hands, without wrath and doubting. (1 Tim 2:8)
Paul expresses the desire for men to pray everywhere. However there is a condition... hands must be holy, sanctified to God - doing His work in a holy way. Clean hands are only required through the Blood of the Lamb, God's only Son who died for the sins of the world. Prayer without wrath and without doubt.