John Gill Commentary Matthew 9:27

"And as Jesus passed by from thence, two blind men followed him, crying out, and saying, Have mercy on us, thou son of David." — Matthew 9:27 (ASV)

And when Jesus departed thence
From the house of Jairus, to another in the same city;

two blind men followed him :
very closely, by the direction of others, having heard of the miracle just now performed by him; and from thence concluded he was able to restore them to their sight;

crying and saying ,
with great faith and fervour, with much importunity, and frequently repeating the following words,

thou son of David, have mercy on us .
From which it appears, that they firmly believed, and were fully persuaded, that he was the true Messiah; for "the son of David" was a known character of the Messiah among the Jews: nothing was more common than to call him by this title, without any other additional epithet, (See Gill on Matthew 1:1), and since it had been prophesied of the Messiah, that he should "open the eyes of the blind", (Isaiah 35:5Isaiah 42:7) they might be greatly encouraged to hope and believe they should obtain mercy from him in this respect.