Worship is an expression of love. To worship in spirit and in truth is simply a sincere expression of love, accompanied by actions and attitudes in keeping with the expression.
If a man says, “I love you” to his wife, when he is carrying on with another lover, his expression of love is meaningless, an insult even.
I think Psalm 51 and Isaiah 58 are excellent chapters on worshipping in spirit and in truth
“Is not this the kind of fasting I have chosen:
to loose the chains of injustice
and untie the cords of the yoke,
to set the oppressed free
and break every yoke?
7 Is it not to share your food with the hungry
and to provide the poor wanderer with shelter—
when you see the naked, to clothe them,
and not to turn away from your own flesh and blood?
8 Then your light will break forth like the dawn,
and your healing will quickly appear;
then your righteousness will go before you,
and the glory of the Lord will be your rear guard.
9 Then you will call, and the Lord will answer;
you will cry for help, and he will say: Here am I. Is 58
Deliver me from the guilt of bloodshed, O God,
you who are God my Savior,
and my tongue will sing of your righteousness.
15 Open my lips, Lord,
and my mouth will declare your praise.
16 You do not delight in sacrifice, or I would bring it;
you do not take pleasure in burnt offerings.
17 My sacrifice, O God, is** a broken spirit;
a broken and contrite heart
you, God, will not despise. Ps 51**