Before he [Paul] sailed, he had his hair cut off at Cenchreae because of a vow he had taken. Acts 18:18
Paul, it seems, took a Nazirite vow (Numbers 6:1-21). This wasn’t to add to his salvation or gain favour with God, instead, he was voluntarily undertaking a spiritual discipline for a specific time and purpose. Perhaps like committing to Lenten studies, a fast or going on a retreat. Spiritual disciplines are valuable if we don’t expect them to entitle us to God’s blessings. They remind us that life isn’t about being focused on our rights and having our way.