ANSWER: Although Marijuana (pot) is not in the Bible per se, we can draw certain conclusions based on Biblical principles. In the book of Ecclesiastes, written by wise King Solomon, it warns us that God takes seriously what we do or do not do.
Have reverence for God, and obey his commands, because this is all that we were created for. 14 God is going to judge everything we do, whether good or bad, even things done in secret (Ecclesiastes 12:13 - 14).
The principles needed to determine if marijuana (pot) is acceptable or not are found in the first and sixth of God's ten commandments. In Exodus 20 these commandments are the following.
"You shall have no other gods before Me."and
"You shall not murder." (The KJV Bible has "thou shalt not kill." Exodus 20:3, 13)
God has given us life. The Bible states he has created certain herbs and plants for eating and healing.
"Every moving thing that lives shall be food for you. I have given you all things, even as the green herbs." (Genesis 9:3, see also Revelation 22:2).
Not every leaf is for eating or healing (or smoking, as in the case of pot), as we certainly would not want to eat poison ivy!
Our bodies are to be treated like the temples of the living God. Although we many times think of a building as being a temple, in God's eyes (especially if we have his Holy Spirit) WE are his temple. The New Covenant, confirmed by Jesus in the New Testament, is an agreement between a human and God where the person promises to live God's way. He looks into the temple as it were (into our character that is inside of us), and welcomes any who, by their thoughts and what they do, keep themselves separate and clean from the ways of the world and Satan the devil, the god of this world (Ephesians 2:1 - 2, 1Corinthians 3:17).
Paul's second letter to the Corinthians states that those who have God's spirit must treat the physical body it currently resides in as a temple. As such, we are to separate ourselves from everything that is unclean and not good for us (both physically and spiritually) so that God our Father can receive us (2Corinthians 6:16 - 18).
The conscience is the key. Here we have seen what the whole duty of man is to the One God who will judge even the hidden things, good or bad, done by all humanity. In addition, there is much scientific and medical evidence concerning the negative short and long-term effects to the human body of smoking pot.