Section 4 in The Indian Contract Act, 1872

4. Communication when complete.—The communication of a proposal is complete when it comes to the knowledge of the person to whom it is made. —The communication of a proposal is complete when it comes to the knowledge of the person to whom it is made.” The communication of an acceptance is complete,— as against the proposer, when it is put in a course of transmission to him so as to be out of the power of the acceptor; as against the acceptor, when it comes to the knowledge of the proposer. The communication of a revocation is complete,— as against the person who makes it, when it is put into a course of transmission to the person to whom it is made, so as to be out of the power of the person who makes it; as against the person to whom it is made, when it comes to his knowledge. Illustrations
   (a) A proposes, by letter, to sell a house to B at a certain price. (a) A proposes, by letter, to sell a house to B at a certain price.” The communication of the proposal is complete when B receives the letter. The communication of the proposal is complete when B receives the letter.”
   (b) B accepts A’s proposal by a letter sent by post. (b) B accepts A’s proposal by a letter sent by post.” The communication of the acceptance is complete, The communication of the acceptance is complete,” as against A when the letter is posted; as against A when the letter is posted;” as against B, when the letter is received by A. as against B, when the letter is received by A.”
   (c) A revokes his proposal by telegram. (c) A revokes his proposal by telegram.” The revocation is complete as against A when the telegram is despatched. The revocation is complete as against A when the telegram is despatched.” It is complete as against B when B receives it. It is complete as against B when B receives it.” B revokes his acceptance by telegram. B’s revocation is complete as against B when the telegram is despatched, and as against A when it reaches him. B revokes his acceptance by telegram. B’s revocation is complete as against B when the telegram is despatched, and as against A when it reaches him.”

Section 5 in The Indian Contract Act, 1872

5. Revocation of Proposals and acceptance.—A proposal may be revoked at any time before the communication of its acceptance is complete as against the proposer, but not afterwards. —A proposal may be revoked at any time before the communication of its acceptance is complete as against the proposer, but not afterwards.” An acceptance may be revoked at any time before the communication of the acceptance is complete as against the acceptor, but not afterwards. Illustrations A proposes, by a letter sent by post, to sell his house to B. A proposes, by a letter sent by post, to sell his house to B.” B accepts the proposal by a letter sent by post. B accepts the proposal by a letter sent by post.” A may revoke his proposal at any time before or at the moment when B posts his letter of acceptance, but not afterwards. A may revoke his proposal at any time before or at the moment when B posts his letter of acceptance, but not afterwards.” B may revoke his acceptance at any time before or at the moment when the letter communicating it reaches A, but not afterwards. B may revoke his acceptance at any time before or at the moment when the letter communicating it reaches A, but not afterwards.”

Section 6 Indian contract act

Revocation how made.—A proposal is revoked— —A proposal is revoked—”

(1) by the communication of notice of revocation by the proposer to the other party;
(2) by the lapse of the time prescribed in such proposal for its acceptance, or, if no time is so prescribed, by the lapse of a reasonable time, without communication of the acceptance;
(3) by the failure of the acceptor to fulfil a condition precedent to acceptance; or
(4) by the death or insanity of the proposer, if the fact of his death or insanity comes to the knowledge of the acceptor before acceptance.

Sample Case: Henthorn v. Fraser (1892) 2 Ch 27