The first occurrence.
And the evening and the morning were the fourth day. Gen 1:19
The primitive root.
Strong’s H7243 רביעי rebiy’iy, an adjective meaning “fourth,” the ordinal of Strong’s H702 ארבע arba, “four,” the cardinal number; from Strong’s H7251 רבע raba, a primitive root meaning, “to square.” The 3 letters resh + bet + ayin tell the parable.
resh ר = head of man, thus head, first, top, beginning, man
bet ב = house, thus house, household, family, in, within
ayin ע = eye, thus watch, know, shade
The story: The head (resh) stone of the house (bet) is the cornerstone, which was always closely watched (ayin) to ensure that it was laid squarely.