Honesty is what demanded from a Civil Servant. A civil servant is employed to help and ensure the provision of basic services to the people. Moreover, it is an important part of his 'duties' to streamline his domain only to serve people. These services should be delivered effectively and efficiently.
He can perform his duties best only when he is the epitome of universally-acknowledged values like honesty, loyalty, courage, hard work and so on. Deviation from such duties only happened when civil servants, instead of inculcating such moral and highly esteemed values in their character, vie for personal gains and enrichment.
Corruption always comes at the altar of honesty. For a man of sense and conscience, it is nearly impossible to bear the guilt of abusing and desecrating fellow-citizens rights.
A civil servant should be a man of conscience and therefore be honest and truthful.