The particle "dei" is used to underscore absolute necessity due to the nature of things. Some New Testament examples include…

Matthew 16:21 "From that time forth began Jesus to shew unto his disciples, how that he must go unto Jerusalem, and suffer many things of the elders and chief priests and scribes, and be killed, and be raised again the third day."

Matthew 24:6 "And ye shall hear of wars and rumours of wars: see that ye be not troubled: for all these things must come to pass, but the end is not yet."

John 3:7 "Marvel not that I said unto thee, Ye must be born again."

John 3:14 "And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up."

John 4:24 "God is a Spirit: and they that worship him must worship him in spirit and in truth."

John 20:9 "For as yet they knew not the scripture, that he must rise again from the dead."

Acts 4:12 "Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved."

Acts 5:29 "Then Peter and the other apostles answered and said, We ought to obey God rather than men."

Acts 16:30-31 "And brought them out, and said, Sirs, what must I do to be saved? And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house."

Acts 17:3 "Opening and alleging, that Christ must needs have suffered, and risen again from the dead; and that this Jesus, whom I preach unto you, is Christ."

1 Corinthians 15:53 "For this corruptible must put on incorruption, and this mortal must put on immortality."

2 Corinthians 5:10 "For we must all appear before the judgment seat of Christ; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad."

1 Timothy 3:2 "A bishop then must be blameless, the husband of one wife, vigilant, sober, of good behaviour, given to hospitality, apt to teach."

1 Timothy 3:7 "Moreover he must have a good report of them which are without; lest he fall into reproach and the snare of the devil."

Hebrews 11:6 "But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him."

Peter 1:6 "Wherein ye greatly rejoice, though now for a season, if need be, ye are in heaviness through manifold temptations."

Revelation 1:1 "The Revelation of Jesus Christ, which God gave unto him, to shew unto his servants things which must shortly come to pass; and he sent and signified it by his angel unto his servant John."