瑜伽論記 4.115

4.115

作意體者，即遍行數，修定慧時作意用增故，對法說：作意增長利益者，謂善順奢摩他、毘鉢奢那故。然明七作意但約定地，四十作意寬通定散地，雖復通定散，而多分依彼位修，故於等引地明之。

As for the intrinsic nature of mental application, it is indeed an omnipresent mental factor. When one cultivates concentration and insight, the function of mental application increases. Hence the Abhidharma states: "The increase and benefit of mental application refers to properly according with śamatha and vipaśyanā." However, the explanation of the seven mental applications is strictly in terms of the concentrated stages, while the forty mental applications broadly extend across both concentrated and unconcentrated stages. Although they extend across both concentrated and unconcentrated states, they are mostly cultivated on the basis of those [concentrated] states; therefore, they are explained in the Stage of Meditative Equipoise.