Truth is the Highest
Living truthfully matters more than any ritual or show of faith.
The true prevails, not the untrue; by the true the path is laid out, the way of the gods (devayânah), on which the old sages, satisfied in their desires, proceed to where there is that highest place of the True One.
अनुद्वेगकरं वाक्यं सत्यं प्रियहितं च यत्।स्वाध्यायाभ्यसनं चैव वाङ्मयं तप उच्यते।।17.15।।
anudvega-karaṁ vākyaṁ satyaṁ priya-hitaṁ cha yat svādhyāyābhyasanaṁ chaiva vāṅ-mayaṁ tapa uchyate
Speech that causes no excitement, is truthful, pleasant, and beneficial; the practice of studying the Vedas is called austerity of speech.
Common thread
All three place truth at the very centre — not only to speak it, but to live it.
Echo
The Upanishad praises Truth; the Guru goes one step further — Truth is good, but truthful conduct is better.
📖 A story to understand
Given money to start a business, the young Nanak spent it feeding starving holy men and called it the ‘True Bargain’ (Sacha Sauda). To him, living honestly and kindly was worth far more than any profit.
Traditional sakhi / story (simplified retelling)