O Israel, trust thou in the Lord - This exhortation is founded in a great measure on what had been just said in regard to idols. They had no power. There was no reason why they should be confided in. They could not help in the day of trouble; and as people need a god, and as the idols cannot be to them as gods, the exhortation is addressed to his people to trust him. He would be to them all that was implied in the name God; all that was wanted in a God.
He is their help - The help of those who trust in him. He is able to help them in the time of trouble; he is willing to help them; he will help them. They who put their trust in him will find him a sure and certain help. This is the experience of all who confide in him.
And their shield - Their protector. See Psalms 5:12, note; Psalms 18:2, note; Psalms 33:20, note. Compare Genesis 15:1; Deuteronomy 33:29; Proverbs 30:5.