The scriptural basis for the translation of bhakti as ‘devotional service’ instead of ‘devotion’
bhaj ity eṣa vai dhatuḥ sevayaṁ parikirtitaḥ
tasmat seva budhaiḥ prokta bhaktiḥ sadhana-bhuyasi
“Bhaj as a root is used to convey ‘service.’ Therefore, the wise explain that engaging in the Lord’s service is the way of bhakti.”
Garuda Purana (Purva-khanda 231.3)