Albert Barnes Commentary Psalms 119:91

"They abide this day according to thine ordinances; For all things are thy servants." — Psalms 119:91 (ASV)

They continue this day according to your ordinances - According to your judgments (Hebrew); that is, your commands. They “stand” (Hebrew) as you have appointed; they are what you designed them to be. The original purpose in their creation is carried out, and they thus furnish an illustration of the stability of your government and the permanency of your law.

For all are your servants - All worlds obey your commands; all are under your control. They show that they are your servants by the conformity of their movements to the laws which you have impressed on them.