na mayy upaisyaty ari-buddhim acyutah
kamsasya dutah prahito ’pi visva-drk
yo ’ntar bahis cetasa etad ihitam
ksetra-jña iksaty amalena caksusa
The infallible Lord will not consider me an enemy, even though Kamsa has sent me here as his messenger. After all, the omniscient Lord is the actual knower of the field of this material body, and with His perfect vision He witnesses, both externally and internally, all the endeavors of the conditioned soul’s heart.
Being omniscient, Lord Krsna knew that Akrura was only externally a friend of Kamsa. Internally he was an eternal devotee of Lord Krsna.