In ‘your’ hands, my dissatisfied fellow-countrymen, and not in ‘mine’, is the momentous issue of civil war. The Government will not assail ‘you’. You can have no conflict without being yourselves the aggressors. ‘You’ have no oath registered in heaven to destroy the Government, while I shall have the most solemn one to “preserve, protect, and defend it.”

Abraham Lincoln (1809-1865) American lawyer, politician, US President (1861-65)

Speech (1861-03-04), Inaugural Address, Washington, D. C.
    (Source)

Lincoln spent most of his first Inaugural addressing the Southern states, trying to forestall their secession. This was the penultimate paragraph (before the "better angels of our nature" one) in the speech as given.

In Lincoln's "First Edition" of the address, a somewhat harsher version of this paragraph was the actual ending of the speech:

In your hands, my dissatisfied fellow countrymen, and not in mine, is the momentous issue of civil war. The government will not assail you, unless you first assail it. You can have no conflict, without being yourselves the aggressors. You have no oath registered in Heaven to destroy the government, while I shall have the most solemn one to “preserve, protect, and defend” it. You can forbear the assault upon it; I can not shrink from the defense of it. With you, and not with me, is the solemn question of “Shall it be peace, or a sword?"

Lincoln offered William Seward, one of his political rivals, an opportunity to review and suggest changes to the draft. Seward offered a number of edits, including in this portion scratching out the last two sentences Lincoln had written, as well as the "first assail" clause.

Seward also added an additional paragraph after this, rather than leaving it as the ending.