Truth of God is One of his Attributes
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Deuteronomy 32:4
He is the Rock, His work is perfect; all His ways are just. A God of faithfulness without injustice, righteous and upright is He.
Isaiah 65:16
Whoever invokes a blessing in the land will do so by the God of truth, and whoever takes an oath in the land will swear by the God of truth. For the former troubles will be forgotten and hidden from My sight.