Genesis 7:9

There went in two and two. In obedience to a mysterious impulse, animals of all kinds moved into the ark. Nothing less than divine power could have effected such a timely and orderly entrance into the huge vessel. What a vivid warning this must have been for the ungodly who witnessed it! Here were domesticated and wild beasts, creeping and flying animals, all making their way into the ark, apparently of their own volition. What a contrast — dumb brutes obedient to their Creator, and intelligent beings refusing to heed His warning call of mercy! If anything could do so, this should have made an impression upon the sinners; but they had hardened their hearts so long that even this miracle left them unimpressed.