Devotional service is the practice of expressing love for the Divine through action: offering work, giving and daily duties with love and reverence. It joins the heart and the hands. For many people it makes spiritual life more concrete, because it asks not only what we believe but also how we serve, speak and care in ordinary hours.
The Gita sums up its teaching in devotional terms. Gita 11.55 says the one who dedicates work to the Lord, holds Him as the supreme goal, is devoted, unattached and free from enmity toward all beings reaches Him, so integrate your work, goals and relationships into a life of devotion. Gita 9.27 invites us to make every act an offering, and Gita 9.26 says that a leaf, a flower, a fruit or water offered with love is accepted, so devotion is open to everyone.
The Gita also describes the quality of devotion. Gita 11.54 says that wholehearted devotion alone reveals, knows and reaches the Lord, so give your deepest commitments undivided attention. Gita 14.26 says unwavering devotion carries one beyond the gunas, and Gita 10.10 says that to the steadfast who worship with love, God gives the wisdom of discernment. Gita 15.19 says true knowledge of the Supreme blossoms into worship, so let your values, work and relationships become expressions of reverence.