I don't remember exactly It was early in the HH series, If i remember right he was talking to either Dorn or Loken but im not certain. I found it online cause i couldn't remember the exact quote
"This planet is a Grave yard- Care to join me?" Techmarine Keilor assigned to the Deathwatch shortly before blowing himself up amid a genestealer cult on Pavia. "Mingle? What in the Emperor's name does that mean?" Priad of the Iron Snakes when invited to a diplomatic reception. "Though my men may sleep, and my ships lay at anchor, my foes know full well that big guns never tire." I can't remember who said that just that it's awesome.
The uniforms of the Imperial Guard are camouflaged in order to protect their wearers by hiding them from sight. The principle is that what the enemy cannot see he cannot kill. This is not the way of the Adeptus Astartes. A Space Marine’s armour is bright with heraldry that proclaims his devotion to his Chapter and the beloved Emperor of Mankind. Our principle is that what the enemy can see, he will soon learn to fear… Chaplain Aston, Fire Hawks 10th Company
"Only a madman knows no fear. A warrior knows what fear is, he feels it in his stomach, he understands fear better than any other mortal can. What makes us strong is that we have conquered fear, overcome it not once but many times, over and over again, until the process has become instinctive. but no matter how many battles you fight and how many victories you win, your fear will never completely leave you. Learn to live with that fear. Learn to master your fear. But never forget that there are things in this universe that even you cannot face and live, abominations so terrible that their very appearance will sear the flesh from your face and shrivel your eyes. Such things cannot be fought, and to confront them would be nothing but a futile waste of life. In those situations remember your vows to serve the Emperor, and remember also that you serve him best alive and not sacrificed upon the altar of vain glory." - Petronius Caligarus, Ultramarines Captain.
"Repent! For tomorrow you die!" "A moment of Laxity spawns a lifetime of Heresy!" "to admit defeat is to blaspheme against the Emperor" Or my favorite "Fear not captain...(bolter shot) i saved you some ork's"
Where there is uncertainty, I shall bring light Where there is doubt, I shall sow faith Where there is shame, I shall point atonement Where there is rage, I shall show its course My word in the soul shall be as my bolter in the field.
Without the Dark, there can be no Light, We have purpose Without the Lie, there can be no Truth, We have purpose Without the War, there can be no Victory, We have purpose Without the Death, there can be no sacrifice, We have purpose Without the Hope there can be no Future, We have purpose Without the Loyalty there can be no one chapter, We have purpose Without the Emperor, there is nothing, ...And we would have no purpose Legiones Astartes Librarius