What does the Bible say about the true nature of fasting?

In Isaiah 58, God clearly defines what constitutes true fasting, emphasizing that it goes beyond bowing one's head or observing pious rituals. True fasting, as God desires, is about loosening the bonds of wickedness, undoing heavy burdens, and letting the oppressed go free. Fasting that is acceptable to God manifests in love and compassion for others, as it aligns with His commandments to love both Him and our neighbors. God is displeased with a self-righteous attitude that expects Him to respond to mere outward displays without a heart of true repentance and godly sorrow.