Douglas Harper's Etymology Dictionary
Wiktionary
vb. 1 (context transitive obsolete English) To show; point out. 2 (context transitive obsolete English) To give; hand over; deliver up; yield. 3 (context transitive obsolete English) To hand over as a trust; intrust; commend, commit (someone), usually as a wish expressed on departing; recommend to the care of; give charge to. 4 (context transitive obsolete English) To commit or commend (one), by the expression of a wish, to (God, the devil, etc.). 5 (context transitive obsolete English) To allot; assign. 6 (context transitive obsolete English) To teach; instruct.
Usage examples of "beteach".
And on the morn he took his leave, and told the king that he would go and seek his brother Sir Lionel, that went from him when that he slept, so he took his horse, and betaught them all to God.
And on the morn Sir Gawaine departed from the hermit, and betaught him unto God.