Our Gemara on Amud Beis tells us about the miracle of the Lechem Hapanim, the bread from the special table in the Beis HaMikdash:

They would lift the table with the shewbread on it to display the shewbread to the oley regel standing in the Temple courtyard, as it was prohibited for Israelites to enter the Sanctuary, where the table stood, and they would say to them: Behold your affection before God, Who performs a perpetual miracle with the bread, for when it is removed from the table on Shabbos  it is just as fresh as when it was arranged on the previous Shabbos . (Every Shabbos the new loaves and frankincense replaced the loaves from the prior Shabbos. The prior Shabbos’ loaves would be removed and eaten by the cohanim, after the burning of the frankincense.) As Rabbi Yehoshua ben Levi said: A great miracle was performed with the shewbread: As its condition during its arrangement, so was its condition during its removal, as it is stated: “To place hot bread on the day when it was taken away” (I Samuel 21:7), indicating that it was as hot on the day of its removal as it was on the day when it was placed.

Tosafos comments on this:

That the miracle really was that it was fresh and soft a week later as it was when it was placed. However the verse that implies it was still hot like when it was baked, is a figure of speech, meaning to say it was fresh. This is because there is an opinion that the bread was baked on Friday before the Shabbos that it was placed (Menachos 95b), and thus it would be impossible for the bread to stay hot until the Shabbos. 

Tosafos seems to be saying that according to the opinion that the baking of the lechem hapanim did not override the rules of Shabbos, the bread was baked on Friday and wouldn’t be hot by the time it was placed on the Shulkhan. So the actual text of the verse in I Samuel 21:7 cannot be literal, as the Bread could not have been hot at the time of the removal in the same way it was hot at the time of his placement, simply because it wouldn’t have been hot either at the time of it’s placement, as it was baked a day earlier on Friday.

The obvious question on Tosafos is once we are discussing miracles, what difference does it really make? If it was a miracle that it would stay fresh for a week that it was on the Shulkhan, why not just as easily say it was baked on Friday, and then became miraculously warm when it was placed on the Shulkhan on Shabbos? (Or, stayed warm from the time it was baked on Friday afternoon. The only reason why I don’t say that is because it might contradict a discussion in Tamid 31b which implies that they specifically used a marble table to hold the bread on Friday afternoon and keep it cool so it wouldn’t spoil. So properly stated, the miracle would have to be cool down on Friday, miraculously become warm on the table, and stay warm throughout the week until next Shabbos.) 

Indeed, the majority of commentaries including Rashi and Ritva (Yoma 21a) Understand the miracle to be literally that the bread remained hot AND fresh, not merely fresh. In fact Ritva goes even further to say that there was a miracle that steam rose from the bread. Otherwise, he says, how would the miracle be apparent to the Oley Regel, since they were viewing the Shulkhan from a distance in the courtyard? They couldn’t see the heat and realize ithat any miracle had occurred? The Chida (Pesach Eynayim Chaggigah) asks this question directly of Tosafos and respectfully disagrees with his premise that additional miracles could not have occurred.

So how can we understand Tosafos? We already have a hint from the Gemara in Tamid 31b that miracles were not always relied upon. Here specifically they used a marble table instead of a metal table in order to prevent both the bread and the meats from spoiling by keeping cool. That is somewhat of a justification for Tosafos’ position that we cannot expect miracles to occur in a broad sense, indiscriminately. Now, we just need a reason to understand conceptually why the miracle would occur if the bread was placed on the Shulkhan immediately when it was hot, that is if it was according to the opinion that it was baked on Shabbos, as opposed to being baked before Shabbos and then it would not for some reason, even by dint of miracle, be able to remain warm until it was placed on the table the next day.

The Zohar (II:155a) notes it is called Lechem Hapanim, literally “bread of the face”, because they draw down sustenance from the countenance above. What does this mean? The Alshich (Vayikra 23:44) Explains that the Shulkhan is a prime example of the principle that spiritual matters from above require an activation from below. איתערותא מתתאה - what is known mystically as an awakening from below. That is, to draw down the spiritual sustenance there needs to be an action taken by making bread below which arouses a spiritual flow from above. I would like to suggest that perhaps the Zohar’s allusion to a heavenly countenance is reminiscent of the verse in Mishley (27:19):

כַּ֭מַּיִם הַפָּנִ֣ים לַפָּנִ֑ים כֵּ֤ן לֵֽב־הָ֝אָדָ֗ם לָאָדָֽם׃

⁦As face answers to face in water, So does one man’s heart to another.

That is, God’s Countenance and blessing is only aroused once it is first greeted by man’s offering.

If This is how we understand the Shulkhan, we can understand the position of Tosafos. Once the bread is on the Shulkhan, a completely different spiritual and miraculous dynamic begins to take effect. We simply cannot expect the same thing to occur to the bread prior to its placement on the Shulkhan. Therefore, Tosafos cannot accept that if the bread is baked on Friday that the warmth would persist miraculously all the way through until the following Shabbos. However, we have no problem with the idea of it staying fresh since it would still be fresh when it would come up on the table and the miraculous dynamic could take effect. Or if it was hot according to the opinion that it was baked on Shabbos and immediately placed on the Shulkhan while it still was hot, then the Shulkhan could take over and activate the miracle. But if the bread came cold to the  Shulkhan, there would be no activation from the physical realm, no איתערותא מתתאה and so no miracle.