The New Testament exhorts us to become bondslaves of the Lord. Paul called himself a willing bondslave of Jesus Christ.
In the Old Testament, there were two classes of servants - the bondslave and the hired servant. A bondslave, unlike the hired servant, was never paid. He was bought by his master for a price - and as a result, all that he was and all that he possessed belonged to his master. This is what every believer must recognise himself to be. Our time, money, talents, families, possessions, minds and bodies - all - belong to our Master and our Lord, for they are His by right of purchase on the Cross (1 Cor. 6:19,20).
In Rom 12:2, we are therefore exhorted to present our bodies to God, once for all, as a living sacrifice, even as the burnt offering in the Old Testament. The burnt offering, unlike the sin offering, was wholly offered to God, and signified the offerer's utter dedication to the Lord. When a man offered a burnt offering, he received nothing back. God could do whatever He liked with that offering. It was symbolic of Calvary's Cross where the Lord Jesus offered Himself utterly to His Father saying, "Father, not My will but Thine be done." This is what it means to present our body as a living sacrifice to God: we must die to our own will and choice as to how and where our body should be used by Him. Only thus can we know His will. Lack of such yieldedness is usually the main reason why we are unable to ascertain God's will. Our yieldedness to the Lord is often with reservations. We are not really willing to accept anything that God may offer.
I met a brother once who was willing to take up any vocation except full-time Christian service. I told him that it was this reservation that kept him from being clear about God's plan for his life. When he finally yielded all to the Lord, he immediately gained a deeper assurance of God's will. God did not call him to full-time Christian service, but He wanted him to be willing.
Many who come to God under the pretext of wanting to know His will really want only His approval of a path they have already chosen for themselves. Hence they receive no answer from Him. How soon our problems of guidance would be solved, if only we gave ourselves without any reserve to our Lord saying, "Lord, I am willing to accept anything, if Thou wilt only assure me that it is Thy will. Choose Thou for me, my Lord. I have no choice of my own in this matter." It was Abraham's willingness to go anywhere and to do anything at any time for God that made him the "Friend of God."
George Muller of Bristol (England) was a man of great faith and one who could ascertain the will of God with remarkable accuracy. He has said in this connection, "I seek at the beginning to get my heart into such a state that it has no will of its own in regard to a given matter. Nine-tenths of the trouble with people is just here. Nine-tenths of the difficulties are overcome when our hearts are ready to do the Lord's will, whatever it may be. When one is truly in this stage, it is usually but a little way to the knowledge of what His will is."
Some want to know God's will first before deciding whether to obey or not. But God does not reveal His will to such people. Jesus said, "If any man desires to do His will, he will know....." (John 7:17). A willingness to do anything that God commands will alone qualify us to know what His perfect will is. This applies to small matters as well as big.