Adam Clarke on Genesis 35:14

A drink-offering - נסך nesech, a libation. These were afterwards very common in all countries. At first they consisted probably of water only, afterwards wine was used; see on Lev 7:1 (note), etc. The pillar which Jacob set up was to commemorate the appearance of God to him; the drink-offering and the oil were intended to express his gratitude and devotion to his preserver. It was probably the same pillar which he had set up before, which had since been thrown down, and which he had consecrated afresh to God.