The English word ‘cherubim’ is a transliteration from the hebrew. The singular hebrew word is cherub, the plural of which is cherubim, so that it is unnecessary, strictly speaking, to add the ‘s’ to form the English ‘cherubims’; it is already plural.
What God commanded to be constructed on earth was to be a representation of what is in heaven, to teach us about heavenly realities. Central to God’s dealings with sinful men and women is the mercy seat. Mercy is essential for us to come to the holy God, and our consciences tell us so with great force. Properly enlightened, our own consciences will not allow us to approach him, for they calculate that if sin comes into his presence then he will certainly destroy it and us. But the mercy seat overcomes not only the reservations and terrors of conscience, but the much greater antagonism of God’s justice to our approach. He who placed cherubim to guard the way to the tree of life, has now placed them to stand over the mercy seat to, as it were, to guide repentant sinners to come for life.