The competency of children under fourteen years of age to testify rests in the discretion of the court, and depends mainly on the moral sense, intelligence and understanding of the individual. It is the intelligence and understanding, and not the age, of the person of tender years, which must govern in determining his competency as a witness. If it be manifestly shown that a child, even six or seven years old, knows the difference between right and wrong, and understands the nature and obligation of an oath, and that he must speak the truth, such child is a competent witness.6 What weight is to be given to the testimony of a boy of such tender years, is a matter for the jury to determine.