"The Lord shut him in." --Genesis 7:16
Noah was shut in away from all the world by the hand of divine love. The door of electing purpose interposes between us and the world which lieth in the wicked one. We are not of the world even as our Lord Jesus was not of the world. Into the sin, the gaiety, the pursuits of the multitude we cannot enter; we cannot play in the streets of Vanity Fair with the children of darkness, for our heavenly Father has shut us in.
Noah was shut in with his God. "Come thou into the ark," was the Lord's invitation, by which He clearly showed that He Himself intended to dwell in the ark with His servant and his family. Thus all the chosen dwell in God and God in them. Happy people to be enclosed in the same circle which contains God in the Trinity of His persons, Father, Son, and Spirit.
Let us never be inattentive to that gracious call, "Come, my people, enter thou into thy chambers, and shut thy doors about thee, and hide thyself as it were for a little moment until the indignation be overpast." Noah was so shut in that no evil could reach him. Floods did but lift him heavenward, and winds did but waft him on his way. Outside of the ark all was ruin, but inside all was rest and peace. Without Christ we perish, but in Christ Jesus there is perfect safety. Noah was so shut in that he could not even desire to come out, and those who are in Christ Jesus are in Him for ever.
They shall go no more out for ever, for eternal faithfulness has shut them in, and infernal malice cannot drag them out. The Prince of the house of David shutteth and no man openeth; and when once in the last days as Master of the house He shall rise up and shut the door, it will be in vain for mere professors to knock, and cry Lord, Lord open unto us, for that same door which shuts in the wise virgins will shut out the foolish for ever. Lord, shut me in by Thy grace.
---from Morning and Evening by Charles Spurgeon