John Gill Commentary Matthew 14:31

"And immediately Jesus stretched forth his hand, and took hold of him, and saith unto him, O thou of little faith, wherefore didst thou doubt?" — Matthew 14:31 (ASV)

And immediately Jesus stretched forth his hand
The Syriac reads it, (htevrbw) , "and in that very moment"; for his case requires immediate assistance, and Christ readily gave it; he reached out his hand at once, being just by him,

and caught him ;
as he was sinking to the bottom, and lifted him up, and set him on his feet upon the water, and enabled him to walk with him to the ship; but not without reproving him for the weakness of his faith,

and said unto him, O thou of little faith :
he does not say, O thou unbeliever! or, O thou who hast no faith! for some faith he had, though but small; of this phrase, (See Gill on Matthew 6:30).

Wherefore didst thou doubt ?
waver, fluctuate, or wast divided between faith and fear. He was worthy of reproof, since he had had the order of Christ to come to him upon the water; and an experience of his power in supporting him thus far; and was now so near unto him, that he had no room to doubt, whether it was he or not, nor of his power to preserve him.