There are many benefits to opening and closing a Bible study with prayer. By means of prayer, we ask Jehovah for his holy spirit on our discussion. (Luke 11:13) Prayer also emphasizes to our student the seriousness of his Bible study and teaches him how to pray. (Luke 6:40) Therefore, it is good to introduce prayer as soon as possible. However, since circumstances vary, the conductor needs to use discernment in deciding whether to offer prayer at a doorstep Bible study.
One important factor to consider is the setting in which the study is held. If there is a measure of privacy, a brief prayer might be discreetly offered to open and close an established study. However, if doing so would draw the attention of onlookers or make the student feel uncomfortable, it may be better to wait until the study can be held in a setting that affords more privacy. Regardless of where the study is held, we should use good judgment to determine when to introduce prayer.