O, Lord of Life and Wisdom, when I realized Thee in my mind as the the First and the Last of Creation, then I found with my inner sight (conscience) that Thou art the Father of Vohuman, the Creator of Truth and the Supreme Judge who justifies the actions of all the living beings.
Yasna 31 Verse 8

One is who led by Thy Holy Spirit lives the best life, his words shall be full of love and wisdom, and his hands shall fulfill the task of Armaiti through faith. His life shall be guided by one single thought that only Mazda is the source of truth.
Yasna 47 Verse 2

Keep hatred and anger far away from yourselves. Let nothing tempt you to violence. Hold on to love and good mind. Brilliant teachers, who wish to hold fast on to truth, shall lead the followers of truth to paradise, Thy abode, O Ahura, where the righteous people dwell .
Yasna 48 Verse 7

O, the Guardian of freedom and worthy of praise, O Lord of Life and Wisdom, I shall gain entrance to Thy Abode with praise and shall join Thee through Truth and Pure Thought. Do guide me, O my Lord, and held me in my tasks.
Yasna 50 Verse 7
Verses from Gathas: The Holy Songs of Zarathushtra
translated by Mobed Firouz Azargoshasb
Ahura means The Lord Creator, and Mazda means Supremely Wise.

As human beings we are given the right to choose. However, because of the law of cause and effect, we are also responsible for our choices, and must face their consequences. 

In other words, having given us the ability to choose, Ahura Mazda leaves us alone and allows us to make our choices. And if we choose good, we will bring about good, and if we choose evil, we will cause evil. This is how the moral universe operates.

Based on the previous principle, we are the causes of all the good and all the evil that happens in our moral universe.

Shahriar Shahriari
Excerpts from the page: Basic Overview of Zarathushtra's Philosphy
at www.zarathushtra.com