Galatians 1: 15-18 But when he who had set me apart before I was born, and who called me by his grace, was pleased to reveal his Son to me, in order that I might preach him among the Gentiles, I did not immediately consult with anyone; nor did I go up to Jerusalem to those who were apostles before me, but I went away into Arabia, and returned again to Damascus. Then after three years I went up to Jerusalem.
The call of God is not a call to any particular service. My interpretation of it may be because contact with the nature of God has made me realize what I would like to do for Him. The call of God is essentially expressive of His nature, not mine. Service is the outcome of what is fitted to my new nature. The vocation of the natural life is stated by the apostle Paul, when he says that “it pleased God to reveal his Son to me, in order that I might preach him among the Gentiles."
Service is the overflow of super-abounding devotion to Christ. There is no direct call to that service. Service is my own response. It is an echo of my having heard His voice, as spoken to Isaiah, “Whom shall I send? And who will go for us?” (6:7) God brings me into a relationship with Himself whereby I understand His call. Then I do things out of sheer love for Him on my own.
To serve God is a deliberate choice, my love-gift to Him. Service is an expression of my new nature in Christ. The Son of God reveals Himself in me, and I serve Him in the ordinary ways of life out of devotion to Him.