Rejoice

This is the day which the Lord has made;
we will rejoice and be glad in it.

Which day are we talking about here? The verse is from the Passover psalm. The "day" is the day on which the Stone which the builders rejected has become the chief cornerstone.

And what does Jesus tell His disciples in the upper room late on Thursday night?

You have heard me say to you,
"I am going away and coming back to you."
If you loved me, you would rejoice
because I said, "I am going to the Father."

He "goes to the Father" on the altar of the cross. He goes to the Holy of Holies with the offering of blood. Even though the disciples would mourn, He knows His suffering is for our rejoicing.