John Calvin Commentary Genesis 24:1

"And Abraham was old, [and] well stricken in age. And Jehovah had blessed Abraham in all things." — Genesis 24:1 (ASV)

And Abraham was old. Moses proceeds to the account of Isaac’s marriage, because Abraham, indeed, perceiving that he was worn down by old age, was determined to ensure that his son should not marry a wife in the land of Canaan.

In this passage, Moses expressly describes Abraham as an old man, so that we may learn that he had been prompted by his very age to seek a wife for his son. For old age itself, which, at the most, is not far from death, ought to lead us to arrange the affairs of our family so that when we die, peace may be preserved among our posterity, the fear of the Lord may flourish, and proper order may prevail.

Abraham's old age was indeed still vigorous, as we shall see later; but when he considered his own years, he deemed it time to make provision for the welfare of his son.

Irreligious men—partly because they do not hold marriage in sufficient honor, and partly because they do not consider the importance attached especially to Isaac's marriage—wonder that Moses, or rather the Spirit of God, should be occupied with such minor matters.

But if we approach the reading of the Sacred Scriptures with due reverence, we shall easily understand that nothing here is superfluous. For since men can hardly persuade themselves that God's Providence extends to marriages, Moses insists all the more on this point.

However, he primarily wishes to teach that God honored Abraham's family with special regard, because the Church was to originate from it. But it will be better to address everything in its proper order.