Isa. 48:18 KJV (With Strong’s)

O that
luw' (Hebrew #3863)
or luw {loo}; a conditional particle; if; by implication (interj. as a wish) would that!
KJV usage: if (haply), peradventure, I pray thee, though, I would, would God (that).
Pronounce: loo
Origin: or lu {loo}
p thou hadst hearkened
qashab (Hebrew #7181)
to prick up the ears, i.e. hearken
KJV usage: attend, (cause to) hear(-ken), give heed, incline, mark (well), regard.
Pronounce: kaw-shab'
Origin: a primitive root
to my commandments
mitsvah (Hebrew #4687)
a command, whether human or divine (collectively, the Law)
KJV usage: (which was) commanded(-ment), law, ordinance, precept.
Pronounce: mits-vaw'
Origin: from 6680
! then had thyq peace
shalowm (Hebrew #7965)
from 7999; safe, i.e. (figuratively) well, happy, friendly; also (abstractly) welfare, i.e. health, prosperity, peace
KJV usage: X do, familiar, X fare, favour, + friend, X great, (good) health, (X perfect, such as be at) peace(-able, -ably), prosper(-ity, -ous), rest, safe(-ty), salute, welfare, (X all is, be) well, X wholly.
Pronounce: shaw-lome'
Origin: or shalom {shaw-lome'}
been as a river
nahar (Hebrew #5104)
a stream (including the sea; expec. the Nile, Euphrates, etc.); figuratively, prosperity
KJV usage: flood, river.
Pronounce: naw-hawr'
Origin: from 5102
, and thy righteousness
tsdaqah (Hebrew #6666)
rightness (abstractly), subjectively (rectitude), objectively (justice), morally (virtue) or figuratively (prosperity)
KJV usage: justice, moderately, right(-eous) (act, -ly, -ness).
Pronounce: tsed-aw-kaw'
Origin: from 6663
as the waves
gal (Hebrew #1530)
something rolled, i.e. a heap of stone or dung (plural ruins), by analogy, a spring of water (plural waves)
KJV usage: billow, heap, spring, wave.
Pronounce: gal
Origin: from 1556
of the sea
yam (Hebrew #3220)
a sea (as breaking in noisy surf) or large body of water; specifically (with the article), the Mediterranean Sea; sometimes a large river, or an artifical basin; locally, the west, or (rarely) the south
KJV usage: sea (X -faring man, (-shore)), south, west (-ern, side, -ward).
Pronounce: yawm
Origin: from an unused root meaning to roar

Cross References

that thou.
then had.

J. N. Darby Translation

Oh that thou hadst hearkened to my commandments! Then would thy peace have been as a river, and thy righteousness as the waves of the sea;