Mahabharata shloka

[thrapp at helios.nosc.mil]

Dear Indologists,

I would like to ask a grammar question about
a shloka from the Mahabharata.

satyasya vacana.m "sreya.h satyAdapi hita.m vadet |
yadbhUtahitamatya.mtametatsatya.m mata.m mama ||

In the second paada, satya appears in the ablative case.
Does this mean that "one should speak what is beneficial
*from* the set of things that are true" or is the ablative
for comparison as in "one should speak what is beneficial
rather *than* what is true"?

Thank you for any help you can provide.

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Gary R. Thrapp
thrapp at nosc.mil