'Unfasten' in the Bible

His announcement was, "There is One coming after me mightier than I--One whose sandal-strap I am unworthy to stoop down and unfasten.

saying to them, “Go into the village in front of you, and immediately as you enter it, you will find a [donkey’s] colt tied, which has never been ridden by anyone; untie it and bring it here.

John answered them all by saying, “As for me, I baptize you [only] with water; but One who is mightier [more powerful, more noble] than I is coming, and I am not fit to untie the strap of His sandals [even as His slave]. He will baptize you [who truly repent] with the Holy Spirit and [you who remain unrepentant] with fire.

He who is to come after me, and whose sandal-strap I am not worthy to unfasten."

But John, towards the end of his career, repeatedly asked the people, "'What do you suppose me to be? I am not the Christ. But there is One coming after me whose sandal I am not worthy to unfasten.'