Commentary for Isaiah 28:16

Behold, I have laid a foundation This is the past tense. Comp. (Esther 1:8) “For so had the king established (יִסַּד).” And so must it be interpreted: Behold, I am He Who has already laid [a stone in Zion. Already] a decree has been decreed before Me, and I have set up the King Messiah, who shall be in Zion as an אֶבֶן בּוֹחֵן, a fortress stone, an expression of a fortress and strength. Comp. (infra 32:14) “A tower and a fortress (וּבֹחֵן).” Comp. also (supra 23:13) “They erected its towers (בַּחוּנָיו).”

הנני יִסַּד I will lay the foundation. יסד is an adjective,¹⁹יסד and שבח, according to I. E., may also be considered as participles of the Piël, the preformative מְ of the Piël and Pual being sometimes dropped. derived from a Piel like אִבַּד he hath destroyed (Lam. 2:9).²⁰The Piël past has two forms, פִּעְל and פִּעַל; it is with the latter that יִסַּד is compared, and therefore אִבַּד is quoted. Comp. Zahoth, On the Piël. Comp. ושבח אני and I praise (Koh. 4:2); which is likewise transitive.

a foundation well founded (מוּסַד מוּסָּד). The first one is voweled with a pattah because it is in the construct state, a foundation of a foundation, which is a solid foundation.