To worship him in truth, one must worship as the apostle John called for in his first epistle:
One must walk as He himself walked.
If one rejects his Biblical Sabbath, or his appointed days, they worship not in truth.
If one keeps not his commandments, one walks not in truth.
If you feel you must in good conscience keep the Sabbath on a Saturday....then you must do so earnestly lest you sin before God by violating your conscience as per the admonition of Paul concerning the keeping of feasts and of Holy days that were sacred to some but not to others! But to others who may read this reply, the keeping of any Sabbath despite the disagreement over the day...is no good without the Lord of the Sabbath indwelling you via the Holy Spirit. When the Lord of the Sabbath is with you, it is Sabbath time forever! Hail the great high priest Jesus Christ after the order of Melchizidek...the Lamb of God that takes away the sin of the world!(That WORD that is God, having been made Flesh that dwelt amongst us...see also 1 John 4 should you have any other issues with what I just said! Yeshua is the Anointed savior made flesh...the begotten son of the Living God!)