The dying man said nothing, only held tightly to his son through most of the night (Para. 7)
Meaning: The dying man did not say anything, only kept his son's hand tightly in his own hand for the greater part of the night.
hold to: keep in understanding, cling to.
This phrase is often used metaphorically. Look at the following examples:
I still hold to my former opinions. 我仍坚持原先的看法。
Do you still hold to your plan of going to Australia? 你是否仍坚持要去澳大利亚?