Q 5: When can a deed be an act of worship?
A--- If there are two things: perfect love (for Allah) along with perfect subjection (to Him).
Allah Almighty says: {But those who believe, love Allah more (than anything else)}. (Al-Baqarah, 165)
Allah the Almighty says: {Verily those who live in awe for fear of their Lord}. (Al-Mu'minun , 57)
Allah the Almighty gathered the two things in the following verse that reads, {Verily, they used to hasten on to do good deeds, and they used to call on Us with hope and fear, and used to humble themselves before Us}. (Al-Anbiya', 90)
Reference: 200 FAQ On Muslims Belief - Shiekh Hafiz Ibn Ahmed Al Hakami