This detailed test for adultery, a "trial by ordeal," is the only one in the Old Testament. Yet, trial by ordeal was common in the ancient Near East. God had a special interest in protecting marriage. It was the foundation of Hebrew society.
The ordeal was intended to promote marital faithfulness. We do not know how often such ordeals actually happened. This procedure relied on God to intervene so that justice occurred when evidence was lacking (see 1 Corinthians 5:5).