'Essential' in the Bible

and so cause them [by neglect of any essential observance] to bear the punishment of guilt when they eat their holy things; for I am the Lord who sanctifies them.’”

O Lord God of hosts, who is like You, O mighty Lord?Your faithfulness surrounds You [as an intrinsic, unchangeable part of Your very being].

The [reverent] fear of the Lord is the beginning (the prerequisite, the absolute essential, the alphabet) of wisdom;A good understanding and a teachable heart are possessed by all those who do the will of the Lord;His praise endures forever.

The inhabitants of one [city] will go to another, saying, “Let us go at once to ask the favor of the Lord and to seek the Lord of hosts. I will go also.”