John Gill Commentary Matthew 26:43

"And he came again and found them sleeping, for their eyes were heavy." — Matthew 26:43 (ASV)

And he came and found them asleep again
For they were aroused and awaked, in some measure, by what he had said to them; but no sooner was he gone but they fell asleep again, and thus he found them a second time; or, "he came again and found them asleep"; so read the Vulgate Latin, the Syriac, Arabic, and Ethiopic versions, and Munster's Hebrew Gospel:

for their eyes were heavy ;
with sleep through fatigue, sorrow Mark adds, "neither knew they what to answer him", (Mark 14:40) ; they were so very sleepy, they knew not how to speak; or they were so confounded, that he should take them asleep a second time, after they had had such a reproof, and exhortation from him, that they knew not what answer to make him; who probably rebuked them again, or gave them a fresh exhortation.