Vishal: Namaste Guruji You are explaining about Ahinsa in Yog Darshan 2.31 in which Patanjali Rishi says Ahinsa should be observed without any condition of class, place, time, and occasion. You said in explanation of this that if anyone says he will do Hinsa for protecting Dev & Brahman (Scholar of Veda and great dignitaries) that mean his Ahinsa condition by occasions. He is not following Yamas properly. Should not one do Hinsa to protect scholar of Veda, cow & country. Why Rishi Patanjali said this?
Swami Ram Swarup: Namasteji. Explanation of Ahinsa has been briefed by Patanjali Rishi correctly. Now question arises to protect the said matter. In this connection, Vedas tell that this is the duty of Government that there must not be any violence in respect of cow, Brahmin and country and other matters. Vedas allow the Government to give punishment and to suppress the culprits at any cost.

Harsh: Pranaam swamiji. Swamiji I am unable to find verses in vedas and upanishads that prohibts adultery and pre-marital sex. People say that vedas encourages it. Can you please tell me in which ved and in which hymn these acts are declared vicious. I will be thankful to you. Saadar charan sparsh swamiji.
Swami Ram Swarup: My blessings to you.

Vedas Prohibit Physical contact before marriage
Yajurved mantra 8/10 says that opposite sex should not love or give heart to each other before marriage and physical contact therefore is strictly prohibited. Secondly to obey the preach of Veda’s is pious act and to go against the Vedas is sin. The result of sin comes in the shape of sorrow, serious disease, tensions, problems or early deaths, etc.

Is to have a relationship before marriage sin?
It is a great sin, please. Yajurved clearly states that a girl or a boy must never give her or his heart to opposite sex and must never even touch each other before marriage i.e., when marriage is fixed and performed completely thereafter only they can meet. So sins create sorrows. To maintain Brahmacharya is the best way to build life strong and to live a long, happy life. You are advised to read my book on Brahmacharya , if possible.

In Vedas, there is a fundamental law, both for boy and girl, that they should never give their heart to opposite sex till marriage. That is why, in the ancient time, marriage based on swayamvar were performed which avoided one sided love too. So please obey the parents otherwise life would be ruined. The human life blessed by God is meant to follow the Vedic path and to do pious deeds and not sins.
As per as adultery is concerned, Yajurved mantra 8/48 refers.