Translated from Latin from the first book of Principia(1687):
Every body preserves in its state of rest or of uniform motion in a right line unless it is compelled to change that state by force impressed thereon.
The alteration of motion is ever proportional to the motive force impressed and is made it in direction of the right line in which the force is impressed.
To every action there is always opposed an equal reaction. Or, the mutual action of two bodies upon each other are always equal and directed to contrary points.
Restated in the modern form:
A particle remains at rest or continues to move in a straight line with a uniform velocity if there is no unbalanced force acting on it.
The acceleration of a particle is proportional to the resultant force acting on it and is in the direction of this force.
The resultant force of action and the resultant force of reaction between interacting bodies are equal in magnitude, opposite in direction, and collinear.