How to treat each other

Beware lest ye harm any soul, or make any heart to sorrow; lest ye wound any man with your words, be he known to you or a stranger, be he friend or foe. Pray ye for all; ask ye that all be blessed, all be forgiven. Beware, beware, lest any of you seek vengeance, even against one who is thirsting for your blood. Beware, beware, lest ye offend the feelings of another, even though he be an evil-doer, and he wish you ill. Look ye not upon the creatures, turn ye to their Creator. See ye not the never-yielding people, see but the Lord of Hosts. Gaze ye not down upon the dust, gaze upward at the shining sun, which hath caused every patch of darksome earth to glow with light. 
- 'Abdu'l-Bahá  (‘Selections from the Writings of 'Abdu'l-Bahá’)

God has “endowed every soul with the capacity to recognize the signs of God”

He [God] hath endowed every soul with the capacity to recognize the signs of God. How could He, otherwise, have fulfilled His testimony unto men, if ye be of them that ponder His Cause in their hearts. He will never deal unjustly with any one, neither will He task a soul beyond its power. He, verily, is the Compassionate, the All-Merciful. 
- Baha'u'llah  (Gleanings from the Writings of Baha'u'llah)

A general rule to guide one’s life...

O thou dear handmaid of God! Thy letter hath been received and its contents noted. Thou didst ask for a rule whereby to guide thy life.

Believe thou in God, and keep thine eyes fixed upon the exalted Kingdom; be thou enamoured of the Abhá Beauty; stand thou firm in the Covenant; yearn thou to ascend into the Heaven of the Universal Light. Be thou severed from this world, and reborn through the sweet scents of holiness that blow from the realm of the All-Highest. Be thou a summoner to love, and be thou kind to all the human race. Love thou the children of men and share in their sorrows. Be thou of those who foster peace. Offer thy friendship, be worthy of trust. Be thou a balm to every sore, be thou a medicine for every ill. Bind thou the souls together. Recite thou the verses of guidance. Be engaged in the worship of thy Lord, and rise up to lead the people aright. Loose thy tongue and teach, and let thy face be bright with the fire of God’s love. Rest thou not for a moment, seek thou to draw no easeful breath. Thus mayest thou become a sign and symbol of God’s love, and a banner of His grace. 
- ‘Abdu’l-Baha  (‘Selections from the Writings of ‘Abdu’l-Baha’)