Hare Krishna Prabhuji
Speaking truth or lie ,that will depend on the circumstances , but on the spiritual platform , Lord says that ,even if one do activities ,which may seem sinful at times (like speaking lie ) on the material platform ,but it will become purified in some cases . But yes ,conditions apply . how ,it is described in the following verse
There is a verse from Padma purana ,where Lord personally says ;
man-nimittam kritam papam
api dharmaya kalpate
mam anadritya dharmo ‘pi
papam syan mat-prabhavatah
“If one sins for My sake his sins become pious deeds. However ,if one refuses to worship Me, then by My power even his pious deeds will become sinful.”
And it is indeed true ,for as far as pious material deeds are concerned ,even if they are performed without any ulterior motives , still it will bind us in this material world ,if one does not .worship supreme lord . However for a devotee ,who always offer everything to lord ,he will not be bound by the burden of either sinful or pious activities ,thus only he can transcend the three modes.
Thus as far as lying is concerned atleast on the material platform ,as you said , it will depend on the circumstances and time , but the point here is that ,if one lies for supreme personality of godhead ,then it will still become purified ,and he will not accrue any sin.
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