"сѧ" meaning in Vieux slave

{
  "categories": [
    {
      "kind": "other",
      "name": "Formes de pronoms personnels en vieux slave",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Vieux slave",
      "orig": "vieux slave",
      "parents": [],
      "source": "w"
    }
  ],
  "derived": [
    {
      "lang": "Polonais",
      "lang_code": "pl",
      "word": "się"
    },
    {
      "lang": "Tchèque",
      "lang_code": "cs",
      "word": "se"
    }
  ],
  "etymology_texts": [
    "Apparenté au latin se."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "pron",
  "pos_title": "Forme de pronom personnel",
  "senses": [
    {
      "form_of": [
        {
          "word": "сєбє"
        }
      ],
      "glosses": [
        "Forme courte de сєбє, accusatif-génitif du pronom personnel réfléchi."
      ],
      "id": "fr-сѧ-cu-pron-LOHLpQoP"
    }
  ],
  "tags": [
    "form-of",
    "person"
  ],
  "word": "сѧ"
}

{
  "categories": [
    "Formes de pronoms personnels en vieux slave",
    "vieux slave"
  ],
  "derived": [
    {
      "lang": "Polonais",
      "lang_code": "pl",
      "word": "się"
    },
    {
      "lang": "Tchèque",
      "lang_code": "cs",
      "word": "se"
    }
  ],
  "etymology_texts": [
    "Apparenté au latin se."
  ],
  "lang": "Vieux slave",
  "lang_code": "cu",
  "pos": "pron",
  "pos_title": "Forme de pronom personnel",
  "senses": [
    {
      "form_of": [
        {
          "word": "сєбє"
        }
      ],
      "glosses": [
        "Forme courte de сєбє, accusatif-génitif du pronom personnel réfléchi."
      ]
    }
  ],
  "tags": [
    "form-of",
    "person"
  ],
  "word": "сѧ"
}