And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good. -- Genesis 1:12 (KJV)
God speaks once on the third day. The ground answers, and Moses records the result with a phrase easy to read past: whose seed was in itself.
Nothing had to be added later. God did not return the following week to instruct the fruit tree on fruit. What the tree would become was already inside what He planted, and the ground brought forth accordingly.
After His Kind
Moses repeats that phrase because it is the point. A seed yields what it is. You cannot lecture a seed into a different harvest, and you do not have to.
There is a warning folded into this and a comfort. The warning is that the harvest tells the truth about the seed. The comfort is larger: when God plants, the outcome does not rest on the quality of your effort. He supplies the life. The ground does what ground does.
Live, Then Walk
Paul lands on the same order in Galatians. “If we live in the Spirit, let us also walk in the Spirit.”
His first clause is settled. He is not asking whether the life is there. He assumes it and then calls for a walk that matches it. The walking does not create the life; it agrees with it. Steps taken in the Spirit are not an attempt to produce something absent but a life behaving like itself.
Much Christian exhaustion comes from getting this backwards, from treating obedience as the seed rather than the tree. God does not ask you to generate what He has already planted. He asks you to live like it is there.
On the third day the ground did not strain. It brought forth what was in the seed, and God looked at it and called it good.