Verse 15: And the LORD spake unto Joshua, saying…
[And He said] More clearly, He had said (Lapide, Masius). Here is narrated at greater length was in verse 11 had been sketched (Masius, Lapide).
Verse 16: Command the priests that bear (Ex. 25:16, 22) the ark of the testimony, that they come up out of Jordan.
[That they ascend from Jordan] Unto the farther bank (Vatablus). They are commanded to ascend, not, to cross. Therefore, who does not see that they stood at the edge of the Canaanite bank, so that, with even with the first step extended beyond the riverbed, they might pass into Canaan (Masius).
Come up out of Jordan: For being now in the middle, and lowest, and deepest place of the river, (of which see on Joshua 3:17,) they are most properly said to ascend or go up to the land; which word is thrice used ill this and the two next following verses.
Verse 17: Joshua therefore commanded the priests, saying, Come ye up out of Jordan.
The priests staid contentedly in the river, till God by Joshua called them out.
 Hebrew: וַיֹּ֣אמֶר יְהוָ֔ה אֶל־יְהוֹשֻׁ֖עַ לֵאמֹֽר׃
 Hebrew: צוֵּה֙ אֶת־הַכֹּ֣הֲנִ֔ים נֹשְׂאֵ֖י אֲר֣וֹן הָעֵד֑וּת וְיַעֲל֖וּ מִן־הַיַּרְדֵּֽן׃
 Hebrew: וַיְצַ֣ו יְהוֹשֻׁ֔עַ אֶת־הַכֹּהֲנִ֖ים לֵאמֹ֑ר עֲל֖וּ מִן־הַיַּרְדֵּֽן׃