פּירוש אויף בראשית 28:18

AND HE SET IT UP FOR A PILLAR. Our Rabbis have explained⁵²Yerushalmi Abodah Zarah IV, 5. the difference between a pillar and an altar by saying that a pillar consists of one stone while an altar is composed of many stones. It further appears that a pillar is made for pouring libations of wine upon it and for the pouring of oil upon it, but not for sacrifices and not for offerings, whereas an altar is for bringing Burnt-offerings and Peace-offerings thereon. When Israel entered the Land, the pillar was prohibited to them⁵³Deuteromony 16:22. because the Canaanites had established it as an ordinance of an idolatrous character to a greater extent than the altars. Even though it is written concerning the altars, Ye shall break down their altars,⁵⁴Exodus 34:13. [since the altars were not as prevalent as pillars among the Canaanites, He did not prohibit the Israelites from making their own altars]. It may be that He did not want to prohibit all sacrifices, and so He retained the altar as fit for libations and sacrifices.

ויצק שמו על ראשה, he anointed it to sanctify it and to make it ready to offer sacrifices on it when he would return to that site. We have such formulations in connection with the sanctification of the various materials donated for the Tabernacle (Numbers 7,1) as well as in Genesis 31,13 and again in verse 22 in our chapter here.

וישכם יעקב....וישם מצבה, he erected the stone to its full height.