Matthew Poole and continuators on Acts 2:26

26 Therefore did my heart rejoyce , and my tongue was glad: moreover also, my flesh shall rest in hope .

Because of Gods nearness to, or presence with him.

Christs and his peoples joy is solid and true, real and inward, and may bear the rest, res severa est verum gaudium.

In the 16. Psalm, ver. 9. 'tis my glory, as the tongue is frequently called; communicating our thoughts or apprehensions by speech, being the excellency of a reasonable Creature.

Or my body:

Or be in the grave, as in a Tabernacle, (ordinarily a moveable, always no durable abiding place)

That is of the Resurrection, and going out of that Tabernacle of the grave.