"A call is always from the Lord. He knows all the world's roads and the needs of all engaged upon them. He continues to work redemption by calling persons to help him in this task. That faith should help, however, is not  what first becomes apparent from the call. 

There are many who hear God's call over and over again without taking it seriously. They have an exact idea of what God does in order to find workers for his vineyard. They can develop theories about the answers of those called and they know precisely what the minimum is that a person can offer God. They also know the maximum. But in all this they close their hearts, as if none of it concerned them personally, as if their role were only to be observers, or at best, witnesses.  They amuse themselves speculating who could be meant, or how this or that one ought to have answered. They would even like to give their dear God advice as to how to make his call even more emphatic and enticing, how to make his language more understandable. Only they themselves do not hear. 

God calls and man has only to listen. The ear which God the Father has given man is capable of receiving the call that goes out from God. But it seems that it is always a long road from the ear to the will and to love. 

God calls in scripture, God calls in sermons, God also calls in every prayer. There is no truly prayed prayer in which his call does not resound. Whether it is the Our Father or the Hail Mary or prayer that one composes: God's voice is always in the background. 

No prayer can be uttered without man's realizing that, in it, God is calling."

                                                                                                 

                                                                                                    --Adrienne von Speyr

                                                                                                    They Followed His Call, 13-14