Isaiah 33:19

You will not see [the] insolent people, [the] people {whose language is too obscure to understand}, [whose] stammering of tongue {cannot be understood}.

Isaiah 28:11

For he will speak with {stammering} and another tongue to this people,

Deuteronomy 28:49-50

Yahweh will raise [up] against you a nation from far [off], from the end of the earth, [attacking] as the eagle swoops [down], {a nation whose language you will not understand},

Jeremiah 5:15

Look, I [am] about to bring on you a nation from afar, house of Israel," {declares} Yahweh. "It [is] an enduring nation, it [is] {an ancient nation}. A nation whose language you do not know, and you cannot understand what they speak.

2 Kings 19:32

" 'Therefore thus says Yahweh to the king of Assyria, "He shall not come to this city, nor shall he shoot an arrow there, nor shall he bring a small shield near her, nor shall he cast a siege ramp against her.

Ezekiel 3:5-6

For you are sent to the house of Israel, not to a people {of obscure speech} and {of a difficult language},

Exodus 14:13

And Moses said to the people, "You must not be afraid. Stand [still] and see the salvation of Yahweh, which he will accomplish for you today, because [the] Egyptians whom you see today you will see never again.

1 Corinthians 14:21

In the law it is written: "By those who speak a foreign language and by the lips of others I will speak to this people, and not even in this way will they obey me," says the Lord.

Treasury of Scripture Knowledge

Summary

Thou shalt not see a fierce people, a people of a deeper speech than thou canst perceive; of a stammering tongue, that thou canst not understand.

Bible References

Shalt not

Exodus 14:13
And Moses said to the people, "You must not be afraid. Stand [still] and see the salvation of Yahweh, which he will accomplish for you today, because [the] Egyptians whom you see today you will see never again.
Deuteronomy 28:49
Yahweh will raise [up] against you a nation from far [off], from the end of the earth, [attacking] as the eagle swoops [down], {a nation whose language you will not understand},
2 Kings 19:32
" 'Therefore thus says Yahweh to the king of Assyria, "He shall not come to this city, nor shall he shoot an arrow there, nor shall he bring a small shield near her, nor shall he cast a siege ramp against her.

Deeper

Isaiah 28:11
For he will speak with {stammering} and another tongue to this people,
Jeremiah 5:15
Look, I [am] about to bring on you a nation from afar, house of Israel," {declares} Yahweh. "It [is] an enduring nation, it [is] {an ancient nation}. A nation whose language you do not know, and you cannot understand what they speak.
Ezekiel 3:5
For you are sent to the house of Israel, not to a people {of obscure speech} and {of a difficult language},
1 Corinthians 14:21
In the law it is written: "By those who speak a foreign language and by the lips of others I will speak to this people, and not even in this way will they obey me," says the Lord.