4:12  

काङ्क्षन्तः कर्मणां सिद्धिं यजन्त इह देवताः ।
क्षिप्रं हि मानुषे लोके सिद्धिर्भवति कर्मजा ॥४-१२॥

kaa~NkShantaH karmaNaaM siddhiM yajanta iha dewataaH ।

kShipraM hi maanuShe loke siddhirbhawati karmajaa ॥४-१२॥

Source: Automatic ITRANS Transliteration

Desirers of achievements from action sacrifice therefor to deities.
Quickly indeed, in this human world, are achievements originated from actions.

Those who sacrifice to deities do so out of desire for achievement from action. Quickly indeed do achievements originate from actions in this human world.

Source: Milind S. Pandit

Those who long for success in their work here (on the earth) worship the demigods (or Devas). Success in work comes quickly in this human world.

Source: The Bhagavad-Gita: The Sacred Song

Men in this world desire success in fruitive activities, and therefore they worship the demigods. Quickly, of course, men get results from fruitive work in this world.

Source: Bhagavad Gita As It Is