Reliability is a part of God's character. It's in the Bible, Psalm 33:4, NIV. "For the word of the Lord is right and true; He is faithful in all He does." Hebrews 13:5, NIV says, "God has said, 'Never will I leave you; never will I forsake you.'"
Christians can be relied on to follow the truth at all times. It's in the Bible, Ephesians 4:15-16, TLB. "Instead, we will lovingly follow the truth at all times—speaking truly, dealing truly, living truly—and so become more and more in every way like Christ who is the Head of His body, the church."