Do we make the Father a liar if we say we have not sinned?
In this theocentric prologue of First John, the author uses the impersonal or royal "we". The "we" are those who are in the Exile (2Kin 17:23-24) and contemplating their host nation's perspective of the Torah.
1Joh 1:5-6 This then is the message which we have heard from the Father, and declare unto you, that YHVH is light, and in Him is no darkness at all. If we say that we have fellowship with the Father, and walk in darkness (emulate our host nation; "darkness" is anywhere outside of the Land of Israel: Isa 9:1-3; 42:6-7,24; 43:5-7; Luk 1:68-79) we lie, and do not the Truth (do not follow the Torah, Psa 119:142; Joh 17:17).
1Joh 1:7-9 But if we walk in the Light as the Father is in the Light, we have fellowship one with another [the remainder of this verse was a scholium, evidently transferred into the text at some stage]. If we who walk in darkness (who imitate our host nation) say that we have no sin, we deceive ourselves, and the Truth (the Torah) is not in us. If we who walk in darkness confess our sins, the Father is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness (transgressions of the Torah, 1Joh 3:4).
1Kin 8:47-53 (Holman Christian Standard Bible) When they come to their senses in the land where they were deported and repent and petition you in their captors' land: "We have sinned and done wrong; we have been wicked," and when they return to you with their whole mind and heart in the land of their enemies who took them captive, and when they pray to you in the direction of their land that you gave their ancestors, the city you have chosen, and the temple I, Solomon, have built for your Name. May you hear in heaven -- your dwelling place -- their prayer and petition, and uphold their cause. May you forgive your People who sinned against you and all their rebellions against you, and may you give them compassion in the eyes of their captors, so that they may be compassionate to them. For they are your People and your inheritance; you brought them out of Egypt, out of the middle of an iron furnace. May your eyes be open to your servant's petition and to the petition of your People Israel, listening to them whenever they call to you. For you, Adonai YHVH, have set them apart as your inheritance from all the people on earth (as you spoke through Your servant Moses when you brought their ancestors out of Egypt).
1Joh 1:10 If we who walk in darkness (who imitate our host nation) say that we have not sinned, we make the Father a liar, and his Word (His Torah) is not in us.