Is saying "na'eeman" to someone who has shaved or trimmed his hair, and responding with "Allah yen'em 'alayk" permissible in Sharia?

It has not been authentically reported from the Prophet (peace and blessings be upon him) that he used to say anything to someone who shaved or shortened his hair. The apparent ruling is that there is no harm in the aforementioned statement, but it should not be taken as a regular custom lest an ignorant person believes it to be a Sunnah.