Albert Barnes Commentary Mark 4:33

"And with many such parables spake he the word unto them, as they were able to hear it;" — Mark 4:33 (ASV)

Spake he the word. The word of God. The doctrines of his gospel.

As they were able to hear it. As they could comprehend it. They were like children; and he was obliged to lead them along cautiously, and by degrees, to a full understanding of the plan of salvation.

as they were able (John 16:12).