I. Small Things in the Sight of Men are Often Big Things in the Sight of God [e.g. a piece of fruit — Adam & Eve, a censer of fire (Nadab & Abihu/ Ahaziah), the offering of a sacrifice (King Saul), the sparing of some animals (King Saul), a hand touching a box (Uzzah), dipping in water (Naaman), a little ‘white lie’ (Ananias & Sapphira); etc.];
II. Big Blessings Come in Things Often Deemed Small by Men [e.g. “What do these feeble Jews?”; “Can anything good come out of Nazareth?”; the widows two mites, etc.];
III. What Appear to Be Small Things to Men are Involved in Obedience to the Gospel, but Our Eternity Depends on Them [Hear-Believe-Repent-Confess-Be Baptized].
Point: Upon those things that men may deem insignificant, God has often placed great importance & held men responsible concerning them. As to worship, when God says "in spirit and in truth" He uses the word "must" stressing the necessity of compliance with these modifying adverbial, prepositional phrases telling us how we are to worship God. These are not negotiable matters — subject to our personal whims or caprices.