Genesi 15:5

And he brought him forth abroad, and said, Look now toward heaven, and tell the stars, if thou be able to number them: and he said unto him, So shall thy seed be.

Ver. 5. And he brought him forth abroad.] Abram having prayed a good part of the day within, is now drawn forth at night to receive the promise. Pray that ye may joy, saith Christ: Joh 16:24 and, if ye will "rejoice evermore," "Pray without ceasing," saith the apostle. 1Th 5:16-17

If thou be able to number them.] Then mayest thou number thy posterity; and they, their privileges. It is God only that "telleth the number of the stars, and calleth them all by their names". Psa 147:4 No man can number them. Jer 33:22 And yet Aratus and Eudoxus vainly vaunted, saith St Augustine, a that they had cast up the stars, and could call them all by their names.

a Aug. De Civ. Dei., lib. xvi.