You ask if there is biblical evidence for the term “High Sabbath.” Well there probably is not the actual term “High Sabbath” besides in St. John where it said, for this day was a “High Sabbath” but the proof lies and basic deduction.
The deduction or subtraction is that Jesus is the Passover and we can agree on that. And if Jesus is the Passover then he would have died on the 14th day of the first month, this being the Passover the year he died and was hung on the cross. So if Jesus died on the Passover, the very next day was a “High Sabbath,” and when we look in the Leviticus chapter 23 the day following the Passover was the feast of unleavened bread (first night), therefore by deduction or by common sense we can conclude that the high day referred to in St. John (chapter 19) is a High Sabbath day of the feast of unleavened bread.
As far as your question saying that the first day of the week two disciples walked with Jesus saying today is the third day since all these things were done and Wednesday crucifixion would be impossible; we will have to refer to what Peter said. The testimonies are stories recounting what took place during Jesus ministry. We have a more sure word of prophecy (2nd Peter 1 v19), meaning the prophecy that the prophets wrote to us is more sure, is more valid, is more concrete than the testimony from the Apostles, because the prophets wrote as they were moved by the Spirit of God.
So we need to understand that what the prophets wrote is more concrete and the prophets wrote that the Messiah (Jesus) would die in the midst of the week. The midst of the week or the middle of the week is Wednesday and three days and three nights from that is when he would rise from the grave.
This would validate Jesus as the Messiah from God because he would be in the grave three nights, Wednesday night Thursday night and Friday night; and Thursday day, Friday day, Saturday day in the grave rising just before sundown on Saturday before the dawning of the sun and so that's how we come to these conclusions.
Please, re-listen to the video and let me know if you have any other questions God bless you!
